Built in 1985 as the Market Post Tower, it was designed to provide a mix of office and retail space.

When first built, the building was controversial due to its gold-colored glass exterior, which produced high light and heat reflection.

Tower 55 remains mixed-use, comprising office, telecom, and retail space, but it is perhaps most well known for its use by internet network service, peering, and colocation providers.

CoreSite, a Denver-based wholesale provider of data centers, colocation and peering, currently handles tenant leases within the building.

[8] The federal Internal Revenue Service (IRS) occupies one entire floor of the building as a regional office.