Inca, California

The same ground, surveyed 44 years apart. Drag the handle to wipe between them. Both sheets are United States Geological Survey originals; neither has been altered.

1942 1986

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.

• 1942 USGS Blythe quadrangle1:250000, 2 printings
• 1945 USGS Midland quadrangle1:62500
• 1952 USGS Midland quadrangle1:62500, 4 printings
• 1954 USGS Salton Sea quadrangle1:250000
• 1955 USGS Salton Sea quadrangle1:250000, 2 printings
• 1959 USGS Salton Sea quadrangle1:250000, 4 printings
• 1963 USGS Salton Sea quadrangle1:250000
• 1965 USGS Salton Sea quadrangle1:250000
• 1983 USGS Inca quadrangle1:24000
• 1986 USGS Blythe quadrangle1:100000, 3 printings

Regional context, not property-specific evidence. The federal mineral resources record lists 17 workings within 5 miles of Inca: 5 past producers, 5 unknowns, 4 occurrences, 2 producers. 2 still produce. What was taken out: Copper, Manganese, Wollastonite, Gold. 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 Riverside County

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

This settlement is recorded in the Geographic Names Information System as feature 243799. 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.

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.