The National Parks Service has charge of 90,540 listings in their register. This is all 50 states, including Alaska and Hawaii and U.S. territories. It includes shipwrecks and lighthouses; historic houses and districts; the white House, the Capitol, and the Supreme Court building.
After careful research beginning as far back as 1954, and ending with Google maps for walking directions so you can examine each site on foot–close up and personal–the final list includes 49,603 total sites: https://www.washingtonpost.com/people/andrea-sachs/?utm_term=.aea354e04d6e
And two maps–one, showing the routes from site to site and two, a colored map showing each state. Utah has many historical sites; Nevada has only a few. The states east of the Mississippi are almost solid color–especially the state of Virginia.
A companion piece maps all of the pubs in the United Kingdom, and 647 historic sites. Take a look.
Historic places include monuments or plaques describing why the site is historic and who is memorialized. It can include cemeteries, railroad sites, Indian excavations–and there will be historic brochures, full-blown histories, sets of photographs, post cards, and slides. While the houses and districts were omitted from the United States maps, these are included in the National Parks register.
Did your family or ancestor have a plaque or monument or history? You probably won’t know until you look! Your favorite genealogist, Arlene Eakle. http://arleneeakle.com.
PS And check out the full article that appeared in the Washington Post written by Andrea Sachs.