The U.S. has more than 180,000 markers telling the nation's story. From the strange to the amazing to the offensive, history is marked for all to see. More than 35,000 groups and individuals have put up markers. Here's some of what they have come up with.

Methodology and sources

The Historical Marker Database was launched by J.J. Prats in 2006. It includes over 180,000 active markers in the United States, contributed by thousands of hobbyists. Anyone who sees a marker can take a photo and submit it to the website. Entries are reviewed by editors to make sure that the marker is permanent, is located outdoors and has information beyond just names, dates and titles. The markers shown here are a sampling of notable signs that caught NPR reporters' attention while researching this project. NPR's analysis of the database for the data points in this story can be accessed here.

• 
•