BlockBefore

Alto, California

41 topographic sheets cover this place, the earliest surveyed in 1897 and the latest in 1995. It stands in the Southeast Marin census division. It lies in ZIP code area 94941. It stands on Ryan Creek. The Survey maps it on the San Rafael quadrangle. 732 people lived here at the 2020 count. It stands 26 feet above sea level.

Alto within Marin County

Then and now

1897 to 1995

The same ground, surveyed 98 years apart. Drag the handle to wipe between them. Both sheets are United States Geological Survey originals; neither has been altered.

Topographic sheet of Alto, surveyed 1995
Topographic sheet of Alto, surveyed 1897

Population over time

2 figures

Alto grew from 711 to 732 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.

YearPeople Change
2010711
2020732+21 (+3%)

Topographic sheets covering this place

17 surveys from 41 printed sheets

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.

Fires near this place

128 since 1992

Regional context, not property-specific evidence. The federal wildfire occurrence database lists 128 fires within 5 miles of Alto between 1992 and 2020, burning about 158 acres in total. 1 started naturally. 6 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.

Reported cause Fires
Missing data/not specified/undetermined78
Equipment and vehicle use17
Recreation and ceremony10
Misuse of fire by a minor7
Arson/incendiarism6
Smoking4
Power generation/transmission/distribution3
Other causes1
Debris and open burning1
Natural1

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

DateCause SizeReported by Name on the report
8 September 2011Missing data/not specified/undeterminedunder an acreMarin County Fire Departmentnot named
7 September 2011Missing data/not specified/undetermined3.0 acresMarin County Fire Departmentnot named
7 September 1992Recreation and ceremonyunder an acreGolden Gate National Recreation AreaLEACH
5 September 2001Missing data/not specified/undeterminedunder an acreGolden Gate National Recreation AreaALTA
3 September 2020Missing data/not specified/undeterminedunder an acreMarin County Fire Departmentnot named
3 September 2007Missing data/not specified/undeterminedunder an acreCalifornia Department of Forestry & Fire Protectionnot named
24 September 1993Power generation/transmission/distribution2.0 acresGolden Gate National Recreation AreaTV#1
23 September 2010Missing data/not specified/undeterminedunder an acreCalifornia Department of Forestry & Fire Protectionnot named

Settlements close enough to share some of these fires:

Every fire recorded in Marin County

Mines and quarries near this place

10 of 20 shown

Regional context, not property-specific evidence. The federal mineral resources record lists 20 workings within 5 miles of Alto: 13 occurrences, 3 producers, 3 unknowns, 1 past producer. 3 still produce. What was taken out: Stone, Crushed/Broken, Manganese, Mercury, Silver. Distance is straight-line from the map coordinates, so a quarry counted here may appear on a neighbouring settlement's page as well.

Where SiteCommodity StatusRecorded
Copperopolis MineAsbestosProducerChrysotile
Fort BakerGold, ManganeseOccurrence1914
GreenbraeSand and Gravel, ConstructionProducer
HotalingStone, Crushed/Broken, Stone, DimensionUnknown
Tiburon Ridge FlagstoneStone, Stone, DimensionOccurrence
ClaimMercuryOccurrence
ClaimMercuryOccurrence
Escalle QuarryStoneUnknown
HotalingStoneOccurrence
Mt TamalpaisSilverOccurrence

Every working recorded in Marin County

Storms near this place

7 since 2010

Regional context, not property-specific evidence. The National Weather Service names Alto in 7 storm reports between 2010 and 2024: 6 flood, 1 flash flood. No death or injury is recorded in these reports. Each account below is quoted exactly as the forecast office filed it, from the NOAA Storm Events Database, and each date opens the federal record of that event.

WhenEvent Place namedHarm What the report says
January 2024FloodAlto$10The offramp from US Highway 101 North to California Route 1 North was closed due to flooding.
January 2023FloodAlto-The underpass of California Highway 1 under US Highway 101 in Manzanita flooded.
January 2021FloodAlto-Flooding on US-101 S and SR 1 off ramp.
February 2019FloodAlto-SB 101 Seminary off ramp flooded.
December 2016Flash FloodAlto-Roadway flooded on ramp at intersection of SR 131 and 101N.
December 2014FloodAlto-Multiple lanes on Highway 101 blocked with flooding.
January 2010FloodAlto-Heavy rain caused flooding on and around State Highway One in Marin City. On and off ramps and most lanes of the highway were closed.

Every storm recorded in Marin County

Nearest settlements

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

Map PlaceDistance Sheets
Homestead Valley0.7 miles41
Strawberry Manor1.0 miles41
Almonte1.0 miles41
Strawberry1.0 miles41
Mill Valley1.0 miles41
Chapman1.1 miles41
Reed1.3 miles41
Bel Aire1.4 miles39

Elsewhere

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.

Wikipedia article on AltoAn encyclopaedic summary. Its text is share-alike, so it is linked here rather than copied.
Wikidata item Q4736768The structured record the population and elevation above come from. Public domain (CC0).

Provenance

This settlement is recorded in the Geographic Names Information System as feature 218191. 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.

Storms. NOAA National Centers for Environmental Information, Storm Events Database https://www.ncei.noaa.gov/stormevents/ A work of the United States government, no copyright under 17 U.S.C. 105. Narratives are quoted verbatim from the National Weather Service report and are not edited or summarised.