This is one of the oldest courthouses in continuous use in Colorado. Its construction took place from 1886 to 1889. Placed on the National Register of Historic Places in 1976, it was designed by the Holmberg Brothers, M. F. Rielly and B. Bradley.
The tower was added in the past few years. I don't think that it does much for the building. This is what it looked like previously:
www.flickr.com/photos/courthouselover/1118408549/ 