- The original construction was in 1916 as a grade separation project to allow Fourth Avenue to pass under the Southern Pacific Railroad
- It was Arizona's oldest underpass at the time and was listed on the National Register of Historic Places in 1988
- The underpass was instrumental in the development of Fourth Avenue as a commercial district, serving as a vital link between the University of Arizona, Fourth Avenue businesses, and downtown Tucson
- The original underpass was demolished in 2008 as part of a $26 million reconstruction project
- The current underpass, completed in 2009, was designed to incorporate modern features such as wider sidewalks, dedicated bicycle lanes, and accommodations for the Tucson Modern Streetcar
- This reconstruction improved connectivity between Fourth Avenue and downtown, as well as enhance safety for various modes of transportation ... the project also included public art installations like a multi-level fountain and sculpture pedestals ... the new underpass has two 14-foot-wide travel lanes, raised sidewalks of varying widths, 6-foot-wide dedicated bike lanes, provisions for the streetcar, and two overhead pedestrian bridges
- Unlike the classical revival style of the original structure, the new underpass features a modern architectural design with rusticated retaining walls and oval-shaped concrete columns
- The underpass is 245 feet long and supports three railroad tracks and Downtown Links
- The Coronado Hotel Apartments are adjacent (northeast), as is The Historic Fourth Avenue Underpass Plaza (northwest)