The district comprises sixty-nine contributing properties in a total area of 27 acres (11 ha) including the Union Depot, Vail Hotel and Quaker Flour Mill.

[3][4] While still South Pueblo, Bat Masterson, best known for his association with Wyatt Earp and Doc Holliday was brought in as sheriff to protect a railroad that was being built.

Local folklore says that in the late 1930s the residents of Union Ave in the mesa junction area petitioned to have the street name changed, in order to avoid association with this element.

In 1939 the upper portion of the street was renamed Colorado Ave.[3] Due to the impacts of negligent ownership and the age of the buildings, decay soon set in.

It has a special significance for Pueblo as it marks the former borders of France and Spain and later United States of America, Mexico and the Republic of Texas.

Annual events held in the district include the "B Street Bash" in June, Oktoberfest in September, and the autumn Pueblo Chile and Frijoles Festival.

The Union Avenue Historic Commercial District was the location of a rally for Barack Obama's presidential campaign on October 31, 2008.