The County Historical Societies often know about most ghost towns. But thedy may want then undisturbed or they may have bulldozed the place. I sometimes find in my research a ghost town they don't know about, but many it only had one
farm & a railroad track. A local library could have an older map or county platbook. Many large cities are putting their old maps & county atlases on line.
A good source is hometownlocator.com/ it lists abandoned or nearly abandoned places, old post office & school & cemetery sites & has new maps, City-data.com has a huge amount of info on every town with 200 or more people in the USA. School addresses, complete motel/hotel listings, street maps & aerial views usually showing most parks. Gives the crime rates for towns, typical weather by month. Often gives date city was incorporated.
map-history.info (not sure if dash is correct) has digital map collections online from many sources.
Wikipedia has major & minor towns & true ghost towns. You can type in any town for info or ghost towns for a specific state. Towns that are near ghost are included with town info for places that never had much population. You can look them up individually or by county, I think. Maybe even by state, not sure. They have links to larger cities website where you might find info on all parks & their rules.
Each state has something called the League of Cities, with a website where you can read lots of helpful info Not sure if there is also a League of Counties? Some small cities that can't afford to get their own website are promoted on county govt site or largest city site. Some states that have many unincorporated places also have a League of Towns with a website.
Some people pass up very old towns because they are too small to be on most maps. Some official highway maps will not show a town if they have no businesses. Some of these places could have a park or old school converted to a residence or storage building.
In an often crowded state like CA, you might try to find old ghost towns or old school sites or old ranch sites, that may have been built over as a park or schoolyard. If there is a small part they didn't use a bulldozer on, could be an old coin.
In some newer areas, it helps to know what year a school or park was built. Many who want old coins only detect the oldest places, or only dig weak beeps. at an old park, that left 75+ year old coins only 3-4" deep. At a 1963 park, I got 11 silver coins. At a 1964 park, I got 3 silver coins. At a 1971 school, I got a 1907-D Barber dime at 2.5". It was in between baseball diamonds in an area that looked as though it was scraped for ice skating. It was also near the old farm house that was demolished to make room for the schoolyard. In a park made about 1990, I got a 1951-D silver dime fairly near a sidewalk & a 1892 Barber Quarter 2.5" deep near a green electrical box. The area was 2 farm houses, but they didn't dare bulldoze to close to the electrical box or the sidewalk.
In 1900, Santa Rosa had a population of 6,673 (I have a huge collection of old & new maps & atlases). Best wishes.
