60 · The Statewide Tier: Fifteen Communities on the Probability Map

The dipping-probability map ranks the probability that arsenical cattle dipping occurred on or near nineteen former ranches in 1907-1915, the practice, never contamination. Only the DOCUMENTED tier is fact; every other tier is graded inference from quarantine-county intensity (USDA Circular 174, 1911: heavy = San Diego, Orange, Ventura, Santa Barbara, San Luis Obispo, Fresno; lesser = LA, Riverside, San Bernardino, Kern, Tulare, Kings, Madera) plus documented cattle operations under the compulsory March 1907 arsenical-dip law. No soil arsenic test for the dip question has been run anywhere in California, and no California test anywhere has targeted the dip signature, arsenic with little or no lead (arsenic trioxide, the cattle-dip poison), as opposed to the lead-arsenate orchard signature (arsenic with lead). This chapter gives each probability-map community one spread. Full rubric and per-ranch rationale: research/statewide/DIPPING_PROBABILITY_RATIONALE.md.

Chapter figures (all communities):

Figure	Path
CA dipping-probability map (tiered, 19 ranches)
research/statewide/CA_dipping_probability_map.jpg
Satellite overview, the tiered communities today
research/statewide/CA_dipping_satellite_overview.jpg
19-tile satellite atlas
research/statewide/CA_dipping_satellite_atlas.jpg
Dipping counties vs modern development
research/statewide/CA_dipping_counties_vs_development.jpg
Arsenic legacy mass-balance model map (MODEL ESTIMATE)
research/arsenic_model/CA_arsenic_legacy_model_map.jpg

San Juan Capistrano

History

• A stockmen's meeting at San Juan Capistrano, January 1908, whose "principal question… had to do with [the cattle tick]", four months before the dipping campaign. [B2, Blade Tribune 18 Jan 1908]
• 600-700 head dipped at Capistrano, May 1908, per Dr. Coleman, deputy state quarantine officer, in the county-ordered program whose documented dip chemistry was "the arsenic preparation recommended by the Government." [B2, LA Herald 27 May 1908; SJ Mercury 26 Jun 1908]
• Inside the 7 March 1912 last-held quarantine district (the Trabuco/Aliso/San Juan Capistrano backcountry), where the dipping obligation persisted longest. [A2, Johnson proclamation]

Dipping evidence tier

DOCUMENTED, named as a 1908 dipping locality in the primary press; the county program was arsenical. The parcel dipped within San Juan Capistrano is unrecorded.

Figures

research/oc_dipping_records/oc_dipping_geography_map.jpg · research/oc_dipping_records/statevet_1912_infestation_map_leaf1181.jpg

Environmental review

Honest limits & counter-evidence

The 1908 site is a locality name, not a parcel, nothing can or should be flagged on the ground. The SLO analog (a county inspector reporting 54-65 vats to his Supervisors in 1908) indicates the granular OC vat list sits in un-digitized county records, not online. Absence of record ≠ absence of fact, and equally, the documented practice implies nothing about residue today.

Yorba Linda / Santa Ana Canyon (Yorba)

History

• "Dipping … in progress at Yorba," May 1908, named in the same deputy-state-quarantine-officer interview as Capistrano and Trabuco. [B2, LA Herald 27 May 1908]
• A dedicated CDNC search for Yorba dipping returns only the 27 May 1908 article itself, no granular Yorba record survives in the digitized press. [B2 + absence of record]
• NE Orange County / Santa Ana Canyon district, cattle driven to the canyon-front ranches. [B2]

Dipping evidence tier

DOCUMENTED, named 1908 dipping locality under the county-ordered arsenical program; no parcel-level detail survives in digitized sources.

Figures

research/oc_dipping_records/oc_dipping_geography_map.jpg · research/statewide/CA_dipping_satellite_atlas.jpg

Environmental review

Honest limits & counter-evidence

The single-article record means the dipping site could lie anywhere in the historic Yorba lands; the community mapping (Yorba Linda / Santa Ana Canyon) is district-level, deliberately imprecise. Un-digitized Santa Ana local press and the county-veterinarian ledger are the only likely sources of finer detail.

Anaheim Hills (Bixby ranch, Santa Ana Canyon)

History

• "Dipping … at the Bixby ranch in Santa Ana canyon," May 1908. [B2, LA Herald 27 May 1908]
• The ranch is independently attested as a real, distinct holding, "a fire Sunday on the Bixby ranch in Santa Ana canyon", separate from the Long Beach Bixby operations. [B2, Enterprise (Riverside) 11 Sep 1907]

Dipping evidence tier

DOCUMENTED, named 1908 dipping locality under the county-ordered arsenical program.

Figures

research/oc_dipping_records/oc_dipping_geography_map.jpg · research/statewide/CA_dipping_satellite_atlas.jpg

Environmental review

Honest limits & counter-evidence

The historic Bixby ranch footprint is mapped only approximately onto modern Anaheim Hills; no vat coordinate exists in any located source. As at every documented site, the fact of the 1908 practice says nothing about soil residue in 2026, that question has simply never been asked of this ground.

Long Beach: Rancho Los Cerritos (documented) + Rancho Los Alamitos

History

• Rancho Los Cerritos (Nieto grant remnant; Temple, then Flint-Bixby): the ranch site museum documents Bixby-era sheep dipping, roughly 1866-1890, the one statewide case of dipping attested at a ranch by an institutional source, but the chemistry is unstated (sheep dips were often lime-sulfur, not arsenic). Subdivision ~1890 ended the sheep era. [B1/C]
• Rancho Los Alamitos (Bixby cattle ranch) straddles the LA/Orange county line, Long Beach, Los Alamitos, Rossmoor, Seal Beach, Cypress. [B1]
• Los Angeles County was a lesser-infested quarantine county under the 1911 federal tiering. [A1]

Dipping evidence tier

Los Cerritos: DOCUMENTED, chemistry unconfirmed (sheep dipping attested; arsenic not established; predates the 1907-1912 program). Los Alamitos: PLAUSIBLE (Bixby cattle ranch, lesser county).

Figures

evidence/images/T09-LOSCERRITOS/USC-CHS_CHS-7411_388c1ad4_adobes_barn_ca1890.jpg (adobes + barn, c.1890) · evidence/images/T09-LOSCERRITOS/HABS_ca0208_011958pv.jpg (Los Cerritos ranch house, HABS) · evidence/images/T10-LOSALAMITOS/Hornbeck_LosAlamitos_LAC_diseno468_preview.jpg (Los Alamitos diseño) · evidence/images/T10-LOSALAMITOS/HALS-CA-90_drawing_00001r.jpg

Environmental review

Honest limits & counter-evidence

The attested sheep-dip era closed ~1890, before the arsenical tick program; measured against that date the unreviewed window is ~37 years. The wetlands reviews index the coastal margin, not the inland Bixby Knolls/Lakewood core (Lakewood, built 1950-54, predates CEQA entirely). Rossmoor and Leisure World likewise predate modern review. Lime-sulfur is the leading alternative chemistry; nothing here establishes arsenic use.

Camp Pendleton (Rancho Santa Margarita y Las Flores)

History

• The giant ocean-front cattle grant, Pico (1845 diseño), Forster from 1864, O'Neill/Flood from 1882, running herds photographed at scale in 1900. [B1/A2, Bancroft land case + CHS photographs]
• San Diego County: heavy quarantine tier, among the very last counties cleared, arsenical dipping the standard method. [A1/B1]
• The federal record's unnamed "one large ranch" (~21,000 head, "lack of co-operation from the owner") is best placed in San Diego County by county-level inference only; Rancho Santa Margarita y Las Flores is a geographically suggestive but unconfirmed candidate, it must not be asserted. [A1/B1 + inference]

Dipping evidence tier

HIGHLY PROBABLE (federal land), heavy county + one of the largest cattle operations on the coast under the compulsory law. No vat located; and the land is a Marine Corps base, not homes (green-ring context on the probability map).

Figures

evidence/images/T13-SANTAMARGARITA/herd_cattle_santa_margarita_1900_CHS-2360.jpg · evidence/images/T13-SANTAMARGARITA/cattle_stream_santa_margarita_1900_CHS-2358.jpg · evidence/images/T13-SANTAMARGARITA/plat_santa_margarita_las_flores_1867_E-1362A.jpg · evidence/images/T13-SANTAMARGARITA/casa_rancho_santa_margarita_HABS_CA-48_015167.jpg

Environmental review

Honest limits & counter-evidence

The separate period item about cattle driven into the surf on an unnamed "17,000-acre ocean-front grant" is a pre-eradication crude method, not a dip-site record. As federal land without housing, the residential-exposure frame that motivates the rest of this report does not apply here; the ranch matters chiefly as the strongest operations-scale candidate in the heavy-county south.

Simi Valley (Rancho Simi)

History

• Rancho Simi (San José de Nuestra Señora de Altagracia y Simi): Pico-family stock from the 1790s; a major cattle enterprise under José de la Guerra (1842-1858); Strathearn ranching era from the 1880s (corral branding photographed c.1915). [B1, Museum of Ventura County / histories]
• Ventura County: heavy quarantine tier; period accounts single out Ventura herds among the most tick-infested when the compulsory arsenical-dip law took effect (MacKellar & Hart 1911, named but not directly retrieved). [A1 / B1]

Dipping evidence tier

LIKELY, heavy county + documented long-running cattle range; no dipping record tied to the rancho by name.

Figures

evidence/images/T03-SIMI/bancroft_diseno_rancho_simi_1842_D-1091.jpg · evidence/images/T03-SIMI/huntington_10756_simi_land_water_1888.jpg

Environmental review

Honest limits & counter-evidence

No vat is named to the rancho; California dipping compelled for scabies often used lime-sulfur, so even a documented dip event would need chemistry confirmation. Parcel-level 1907-1912 land use is unrecorded.

Fillmore (Rancho Sespe)

History

• Rancho Sespe (also recorded as "San Cayetano"), Ventura County; land-grant claim filed 1852 (Bancroft land case). [A2, Bancroft]
• Cattle range in a heavy quarantine county, then an early, thorough conversion to citrus: by the 1910s-1920s Rancho Sespe was a major citrus operation (nursery and packing-house photographs, 1914-1926). [A1 tiering / B1 archival photographs]

Dipping evidence tier

LIKELY, heavy county (Ventura) + documented cattle range (later citrus); no dipping record by name.

Figures

evidence/images/T07-SESPE/diseno_B-990_bancroft_78806.jpg · evidence/images/T07-SESPE/postcard_sespe_river_fillmore_front_203657.jpg

Environmental review

Honest limits & counter-evidence

The citrus conversion is genuine counter-evidence for interpreting any future arsenic detection, orchard chemistry (As with Pb) would be the null explanation, and only the Pb ratio distinguishes it from dip residue. No vat, no test, no claim.

Rancho Santa Fe / Del Mar / Solana Beach (Rancho San Dieguito)

History

• Osuna grant (1840s): hide-and-tallow, open-grazing cattle rancho watered by the San Dieguito River and springs, grazed by Osuna heirs into the late 1800s. [B1]
• AT&SF railway interests acquired the tract c.1906; Rancho Santa Fe platted 1922 (Santa Fe Land Improvement Co.), Del Mar 1885/1908, Solana Beach 1920s, all decades before CEQA (1970) and before Phase I ESA practice. [B1]
• San Diego County: heavy tier, among the last four counties under quarantine (1 Apr 1910), white arsenic + soda + pine tar the permitted formula (1910). [B1, Pulling 1965]

Dipping evidence tier

LIKELY, heavy county + century-scale cattle range; built pre-CEQA (never reviewed); no vat named.

Figures

evidence/images/T06-SANDIEGUITO/HABS_ca1694_RanchoSantaFe_036660.jpg (HABS, Rancho Santa Fe; series 036660-036668 in the same directory)

Environmental review

Honest limits & counter-evidence

No dipping record names the rancho; the CDNC search was not exhaustive (403s to automated query). Del Mar's coverage on the 1901 topo sheet is unconfirmed. "Never reviewed" describes an administrative gap, not a hazard.

Rancho Bernardo (Rancho San Bernardo)

History

• Rancho San Bernardo (Snook grant); the 1893 USGS Escondido topo, which predates the mandated-dipping era, labels "San Bernardo." [A1/B1]
• Master-planned 1962 (Hawn & Summers / Charles Luckman) and built largely 1962-1984 under AVCO, before CEQA (1970/1972). [B1]
• San Diego County: heavy tier; mandated arsenical dipping well established at county scale ~1907-1912, with county quarantine dates possibly running to ~1917. [B1]

Dipping evidence tier

LIKELY, heavy county + cattle range; built pre-CEQA; no vat named ("NONE BY NAME" is the plain-language record finding).

Figures

evidence/images/T05-SANBERNARDO/diseno_D-1387_San_Bernardo_Bancroft.jpg · evidence/images/T05-SANBERNARDO/Emory_1847_San_Pasqual_battle_sketch.jpg

Environmental review

Honest limits & counter-evidence

Several potentially relevant sources (a 6 MB ranching-survey scan; a nearby Phase I) are image-only PDFs that could not be text-searched; CDNC returned 403 to automated query. Both photographic records bracket the dip era without covering it: the 1893 topo is too early, the earliest usable inland aerial too late.

Rancho Peñasquitos / Mira Mesa / Carmel Valley (Rancho Santa Maria de Los Peñasquitos)

History

• An 1823 Mexican grant (~8,486 ac) on Los Peñasquitos Canyon and its perennial creek, expanded 1834; restocked 1921, and by 1962 described as "one of the largest cattle ranches in Southern California." [B1]
• The documented working core (adobe ranch house, corrals) lay along the canyon near today's Preserve, not necessarily under the modern residential footprints. [B1]
• San Diego County: heavy quarantine tier. [A1]

Dipping evidence tier

LIKELY, heavy county + large, water-favored cattle operation; terrain-plausible working facility; no dip record by name (the place-name "Penasquitos" appears on only 7 pages in the entire digitized national newspaper corpus, too sparse to be probative either way).

Figures

evidence/images/T04-PENASQUITOS/habs_ca2072_house_photo1_015244.jpg (Johnson-Taylor adobe) · evidence/images/T04-PENASQUITOS/habs_ca2072A_barn_photo1_015247.jpg (ranch barn, HABS)

Environmental review

Honest limits & counter-evidence

California dipping was driven by episodic quarantines, not the permanent vat network of the Gulf South, the prior for a fixed vat is genuinely lower. Topo maps reach 1901/1903 but cannot resolve a working corral or vat.

Rancho Cucamonga

History

• Rancho de Cucamonga: 13,045 ac granted to Tiburcio Tapia, 1839, began as hide-and-tallow cattle, then converted early and intensively to vineyards (California's first commercial-winery district) and citrus/olives, well before the arsenical-dip era. [B1]
• San Bernardino County: lesser quarantine tier. [A1]

Dipping evidence tier

PLAUSIBLE, lesser county; cattle era largely pre-dated the program; the dominant land use in the dip window was orchard/vineyard, which lowers the prior for an arsenical cattle dip here.

Figures

evidence/images/T11-CUCAMONGA/Huntington_SolanoReeve_MapOfRanchoCucamonga_S71_1893-11_id12929.jpg · evidence/images/T11-CUCAMONGA/Huntington_SolanoReeve_CucamongaCreek_1870-1880_id11383.jpg

Environmental review

Honest limits & counter-evidence

This is the statewide set's clearest case where the competing orchard-arsenic vector better explains any arsenic that might ever be found. No vat is named; CDNC/Chronicling America returned 403 to automated query, so the newspaper negative is bounded.

Jurupa Valley / Riverside (Rancho Jurupa)

History

• Rancho Jurupa: 40,569 ac granted to Juan Bandini, 1838, straddling the Santa Ana River; under Louis Rubidoux, "one of the most prosperous stock raisers in Southern California", plus orchards, vineyards, grain, a grist mill. [B1]
• Riverside County: lesser quarantine tier. [A1]

Dipping evidence tier

PLAUSIBLE, lesser county + intensively stocked river rancho; perennial water and sustained herds make a working facility plausible in the abstract; nothing is named.

Figures

evidence/images/T12-JURUPA/CHS-8976_rubidoux-ranch-house-ca1869.jpg · evidence/images/T12-JURUPA/CHS-12796_rubidoux-rancho-blacksmith-shop-1960.jpg

Environmental review

Honest limits & counter-evidence

One parcel's documentary reconstruction (undeveloped land → agriculture from 1938 → lumber yard) constrains nothing about a 40,000-acre grant. California's dip-vat density was lower than the Southern fever-tick states, the "no named vat" result is weaker evidence here than it would be in Florida.

Valencia / Santa Clarita (Rancho San Francisco → Newhall Ranch)

History

• Rancho San Francisco, later the core of the Newhall Ranch / Newhall Land and Farming Company, northwestern LA County along the Santa Clara River. [B1]
• Los Angeles County: lesser quarantine tier. [A1]
• Uniquely in this set, the land carries a large, modern CEQA record: Specific Plan FEIR (2003), RMDP-SCP EIS/EIR (2010), and multiple ASTM Phase I ESAs. [A2]

Dipping evidence tier

PLAUSIBLE, lesser county, cattle range; and a competing orchard-arsenic vector: the arsenic screening that exists here was orchard/row-crop-driven, not dip-driven.

Figures

evidence/images/T08-NEWHALL/WikimediaCommons_RanchoSanFrancisco_diseno_map_1843_PD.jpg · evidence/images/T08-NEWHALL/HABS_ca1195_RanchoCamulos_020244.jpg

Environmental review

Honest limits & counter-evidence

The earliest aerials of this land (~1927) postdate dipping's end, so even these extensive reviews could not see the dip era; the exact earliest-aerial year each Phase I reached is not printed in the searchable text (~1927 is the archive floor, not a quoted review floor). Any arsenic found by the 2013 program has an orchard-first explanation.

Tejon (Tejon Ranch, Lebec)

History

• Tejon Ranch (Rancho El Tejón and associated grants): Edward F. Beale's vast Kern County holding; a working cattle empire into the modern era, mid-century operations fed 12,000 head across ~298,000 acres. [B1, LOC/Huntington photographic record]
• Kern County: lesser quarantine tier; the ranch remains largely unbuilt today. [A1 / B1]

Dipping evidence tier

PLAUSIBLE (unbuilt), huge cattle operation, but a lesser-infested county, and the land is mostly not under housing (green-ring context).

Figures

evidence/images/T14-TEJON/LOC_2002706073.jpg and companion LOC photographs (1888-1890) and Fort Tejon HABS documentation in evidence/images/T14-TEJON/, item-level attribution in research/statewide/IMAGE_INDEX.md.

Environmental review

Honest limits & counter-evidence

Interior-Kern tick pressure is less documented than the coastal south. The Tejon Ranch Company records, 1912-1945 (Sherman Library, incl. 169 photographs), are the archive most likely to name any working/dipping facility, unexamined.

Miller & Lux (Los Baños / San Joaquin Valley)

History

• Miller & Lux ran one of the largest integrated cattle enterprises in the American West, with San Joaquin Valley holdings across Stanislaus, Merced, Fresno, Kings, and Kern counties (1935 corporate cadastral map) and its operational heart near Los Baños. [B1/A2, corporate maps]
• Fresno County: heavy quarantine tier, but tick persistence in the hot interior valley is less certain than on the coastal ranges. [A1 / inference]
• The land today is overwhelmingly farmland, not master-planned housing. [B1]

Dipping evidence tier

PLAUSIBLE (farmland), large cattle operation in a heavy county, discounted for uncertain valley tick ecology and for the absence of a residential build-out.

Figures

evidence/images/T15-MILLERLUX/LOC_KernCounty_ranches_1888_britton-rey.jpg (1888 Britton & Rey ranch-lands map)

Environmental review

Honest limits & counter-evidence

The corporate archives (Bancroft Miller & Lux records; the Huntington's Latta collection; UC Davis) are the record class that could name working facilities across the holdings, none examined here. Dispersed holdings across five counties mean "Miller & Lux" is an enterprise, not a single testable site.

What would change any tier

A named arsenical dip record (e.g., a county-veterinarian vat list) promotes an inference tier to DOCUMENTED. A soil arsenic test, distinguishing the lead-arsenate orchard signature from the arsenic-trioxide dip signature, is the only act that speaks to residue, and it has been run for the dip question nowhere in California. These tiers are a research prioritisation, not a statement about any community.

This platform is an independent research and data-organization project. It does not provide medical advice and does not establish that any pesticide, property, organization, employer, school, water provider, government agency, or other party caused any illness. Publicly reported health events may not have been independently medically verified. Geographic and temporal overlap does not establish exposure or causation. Formal conclusions require authorized epidemiological analysis, verified medical information, exposure assessment, toxicological review, and independent scientific evaluation.