Flagstaff Mountain was named for the flagpole which sits atop its summit (at 6,850 feet), visible when Boulder was first settled as a treeless plain. Also on top of the summit is the Flagstaff Nature Center, a great place to become familiar with the local wildlife and plants as well as the history of Boulder's Open Space and Mountain Parks.
In 1922 (back when Colorado was a Ku Klux Klan stronghold), the KKK staged a parade down Pearl Street, then set fire to a cross on
Flagstaff Mountain's summit. (It seems members of the KKK aren't keen on scratching below the surface: the Klan returned to the city to host
a rally in 1994 and congratulated Boulder [a.k.a. "The People's Republic of Boulder," a city that prides itself on being one of the most
progressive in the nation] for its demographics: Boulder is almost 90 percent white.)