Before visiting Denver, read up on the history of the city and the state in advance.  A little knowledge of the characters and events that helped shape our state will make a visit here that much more interesting and meaningful.

Who was Baby Doe Tabor?  Why did the Central City Opera commission an opera about her life?  Why is Leadville, a small mountain town today, so important in Colorado history?  What theatre in Denver was once called "one of the cradles of American drama" by Cecil B. Demille?

Dr Tom Noel, a Denver professor of history locally known as "Dr Colorado" has authored or co-authored several interesting books on the history of Denver and Colorado including:

The City and the Saloon: Denver, 1858-1916  This book examines the city's history and how it can hardly be separated from the history of its (many) saloons....

Denver: The City Beautiful and Its Architects (by Noel and Barbara Norgren)

His books are a good start.  On his website, he also has his own list of suggested readings about Denver and Colorado

The theatre mentioned by Cecil B. Demille, by the way, is the Elitch Theatre in NW Denver, located on the property of the former Elitch Gardens (now a Six Flags amusement park).  A good book on the subject is:

Denver's Elitch Gardens, Betty Lynne Hull