Sand Creek Massacre National Historic Site
Place in Colorado listed on National Register of Historic Places.
Each edition grades its towns against each other only.

For a trip from Holly, Fort Lyon is 55 mi away. All of it lies outside: 2 places within 40 miles, none inside Holly. Visits to Amache National Historic Site run to about 8K a year.

National Historic Site of the United States in Colorado.
The towns around it, and where to stay →
Sand Creek Massacre National Historic Site, 38 mi away, is the farthest on the map.
Orange: Holly. Numbers: the best-known places, matching the list below. © OpenStreetMap contributors
You will find all 3 within 60 miles.
Place in Colorado listed on National Register of Historic Places.
National Historic Site of the United States in Colorado.
Ranked by how many people look them up, so the famous places lead and the local favorites follow.
Sand Creek Massacre National Historic Site: Plazak at English Wikipedia, CC BY-SA 3.0 · Amache National Historic Site: Tom Parker, Public domain · Fort Lyon: Jeffrey Beall, CC BY 3.0