Blackhawk, California

The same ground, surveyed 93 years apart. Drag the handle to wipe between them. Both sheets are United States Geological Survey originals; neither has been altered.

1896 1989

Blackhawk grew from 9,354 to 9,637 between 2010 and 2020. These are the recorded population figures Wikidata holds for this place, reached through the Geographic Names Information System number this page is keyed on rather than by name, so they belong to this place and not to another of the same name. Most are census counts, but not all are: an early figure may be a founding or settlement estimate, and an estimate published within five years of a census is left out. The change column is computed, and is left blank where more than 20 years separate a figure from the one before it, because a gap that long is not a change between two counts.

Matched by testing this settlement's coordinate against the published boundary of every sheet in the United States Geological Survey's historical collection. Each opens the scanned sheet at the Survey.

• 1896 USGS Mt. Diablo quadrangle1:62500
• 1898 USGS Mt. Diablo quadrangle1:62500, 7 printings
• 1943 USGS Mt. Diablo quadrangle1:62500
• 1947 USGS San Jose quadrangle1:250000
• 1953 USGS Diablo quadrangle1:24000, 9 printings
• 1956 USGS San Jose quadrangle1:250000
• 1962 USGS San Jose quadrangle1:250000, 4 printings
• 1966 USGS San Jose quadrangle1:250000
• 1989 USGS Stockton quadrangle1:100000, 2 printings

Regional context, not property-specific evidence. The federal wildfire occurrence database lists 141 fires within 5 miles of Blackhawk between 1992 and 2020, burning about 674 acres in total. 1 started naturally. 14 were recorded as arson. Distance is straight-line from the map coordinates, so a fire counted here may appear on a neighbouring settlement's page as well.

The most recent of them, most recent first, with the day each was reported and the service that recorded it.

Settlements close enough to share some of these fires:

• Diablo
• Alamo Oaks
• Danville
• Rock City
• Camino Tassajara
• Alamo

Every fire recorded in Contra Costa County

Regional context, not property-specific evidence. The federal mineral resources record lists 19 workings within 5 miles of Blackhawk: 7 prospects, 5 past producers, 4 occurrences, 2 unknowns. 1 still produces. What was taken out: Sand and Gravel, Construction, Asbestos, Copper, Manganese. Distance is straight-line from the map coordinates, so a quarry counted here may appear on a neighbouring settlement's page as well.

Every working recorded in Contra Costa County

The eight closest, with where each one stands in the county. Distances are straight-line, computed from the Geographic Names Information System coordinates.

Matched on this settlement's Geographic Names Information System number rather than its name, so it cannot be a different place of the same name in another state.

This settlement is recorded in the Geographic Names Information System as feature 1867000. The sheet list is computed by point-in-boundary test against the United States Geological Survey's historical topographic inventory. Both are works of the United States government and carry no copyright under 17 U.S.C. 105.

Wildfire. Short, Karen C. 2022. Spatial wildfire occurrence data for the United States, 1992-2020 [FPA_FOD_20221014]. 6th Edition. Fort Collins, CO: Forest Service Research Data Archive. https://doi.org/10.2737/RDS-2013-0009.6 Collected with United States Government funding and usable without additional permissions or fees.

Mines and quarries. USGS Mineral Resources Data System (MRDS) https://mrdata.usgs.gov/mrds/ A work of the United States government, no copyright under 17 U.S.C. 105.