Got into a debate with a friend on whether or not it was legal for me to ride my bicycle on the sidewalk.

According to Denver bicycle ordinances, it is illegal for me to ride my bicycle on a sidewalk except under specific situations:

Sec. 54-576. Riding on sidewalks.(a) Riding bicycles upon or along sidewalks, whether on public property or private property opened for use by the general public, shall be unlawful except when the operator or rider thereof is a uniformed city employee riding a bicycle or a police officer riding a bicycle is a marked or unmarked official police bicycle while engaged in the discharge of his or her official duties, or when the operator or rider thereof is engaged in the delivery of newspapers or where the sidewalk is part of a designated bicycleroute. Bicyclists shall yield the right-of-way to pedestrians on the sidewalks, and shall leave the sidewalk or dismount if necessary to yield such right-of-way.

(b) Riding motorized bicycles upon or along sidewalks shall be unlawful.

(Code 1950, §§ 522.19-1, 522.19-2, 852.5; Ord. No. 464-02, § 1, 6-17-02)

So, unless I am a police officer, delivering newspapers, or following a designated bicycle route, it is unlawful of me to ride on the sidewalk. The only condition that ever applies is the bicycle route part (which is rarely).

Another interesting ordinance:

Sec. 54-565. Application of traffic laws.Every person riding a bicycle or motorized bicycle upon a roadway shall be granted all of the rights and shall be subjected to all of the duties applicable to the driver of a vehicle by the traffic rules and regulations of this city applicable to the driver of a vehicle, except as to special regulations and except as to the provisions of laws and ordinances which by their nature can have no application.

(Code 1950, § 522.11)

In other words, I have a right to ride on the same road as you drive.

Source: Denver Bicycling Ordinances