Do you men "historic" landmark? Any building can be a landmark, even an outhouse.
Fort Ross is located in Sonoma County, California and was built in 1812. It was originally called Fortress Ross. Fort Ross is a U.S. National Historic Landmark.
Fort Fisher was created in 1861.
The Chicago Water Tower, and according to Wikipedia's list -- below -- the Eads Bridge and the Fort Sheridan Historic District.
A building called the "old fort" is the oldest building in the state of Montana. The "old fort" is located in Fort Benton and it is considered a national landmark.
Second Battle of Fort Fisher happened in 1865.
Billy Bob's Texas nightclub is located in Fort Worth Stockyards, Texas. Fort Worth Stockyards is a historic district which itself is a notable landmark and definitely worth checking.
Fort Fisher State Recreation Area was created in 1986.
First Battle of Fort Fisher happened on 27-12-23.
Fort McAllister Historic Park was created in 1861.
Fort Mitchell Historic Site was created in 1813.
Fort Hunter Historic District was created in 1760.