Site Navigation Arizona Colorado Idaho Montana Nevada New Mexico Utah Wyoming     Interstate 25 Routing Interstate 25 is the main north-south freeway corridor through Colorado. Part of the Camino Real High Priority Corridor, Interstate 25 connects Mexico with Canada via ports at El Paso and a connection with Interstates 15 and 90 to Canada. The freeway is undergoing several improvements as part of this corridor strategy, including the massive T-REX improvement project in Denver, upgrades through Colorado Springs, and planned expansion of the freeway to six lanes along the Front Range. Once completed in Colorado, Interstate 25 replaced U.S. 87. That route is silently merged with Interstate 25 for most of its length in Colorado. There are a handful of U.S. 87 shields, and a fun game may be to find the three or so shields for U.S. 87 that remain on Interstate 25. U.S. 87 does not appear on any overhead signs in Colorado. Index The following counties are profiled along the Interstate 25 corridor in Colorado: Northbound Interstate 25 - El Paso County Interstate 25 - Douglas County Interstate 25 - Arapahoe County Interstate 25 - Denver County Interstate 25 - Adams and Broomfield Counties Interstate 25 - Weld County Interstate 25 - Larimer County/N.W. Weld County Southbound Interstate 25 - Larimer County/N.W. Weld County Interstate 25 - Weld County Interstate 25 - Adams and Broomfield Counties Interstate 25 - Denver County Interstate 25 - Arapahoe County Interstate 25 - Douglas County Interstate 25 - El Paso County History Interstate 25 was the first mainline Interstate highway to be completed in Colorado. It was also the first segment of freeway to be built in Colorado. Known as the Valley Highway (U.S. 87), the first two-mile section of future Interstate 25 began construction in August, 1948, and was completed in 1950. By 1958, the Valley Highway through the Denver metropolitan area was completed, only two years after the Interstate Highway Act was signed by President Eisenhower. Another pre-Interstate section of Interstate 25 that was grandfathered into the system included a 9.2-mile segment of freeway in Pueblo (construction began in 1949 and was completed in 1958). A notable milestone in the construction process was the extension of Interstate 25 into Wyoming on October 11, 1964. This date marked the first occasion when a Colorado Interstate actually crossed state lines and entered another state. A 26-mile segment of Interstate 25 heading north from Wellington opened on that date. Segment Location/Description Mileage (Approximate) Completion Trinidad/Raton Pass From Raton Pass at New Mexico Line north to south edge of Trinidad 13 miles 1966 Trinidad Elevated portion, approximately three miles in length 3 miles 1963 Trinidad to Walsenburg From Trinidad north to Walsenburg. This was the last segment of I-25 to be completed in Colorado ; it was dedicated on 9/21/69 21 miles 1969 Walsenburg Constructed as the Walsenburg Bypass 3 miles 1964 Walsenburg to Colorado City Connects north end of Walsenburg bypass with Colorado 165 interchange 22 miles 1968 Colorado City From Colorado 165 interchange in Colorado City north to Pueblo Boulevard 20 miles 1965 Pueblo Original urban freeway segment of Interstate 25 near downtown Pueblo ; includes 0.6-mile long bridge over Arkansas River 9.2 miles July 1959 South of Pueblo to Monument From south of Pueblo to north of Colorado Springs; connected pre-existing segments in Pueblo and Colorado Springs 67 miles 1961 Colorado Springs Original urban freeway segment of Interstate 25 near downtown Colorado Springs 12 miles July 1960 Monument Hill Monument to Larkspur 12 miles 1965 Larkspur to Castle Rock   9 miles 1968 Castle Rock to Denver Connects Castle Rock with Valley Highway in Denver 25 miles 1963 Denver From Evans Avenue north to 48th Avenue . This urban freeway was first section of Interstate 25 built; it was known as the Valley Highway (U.S. 87) 11.2 miles November 1958 Denver Northside From the north end of the Valley Highway (at 48th Avenue ) north to 58th Avenue 0.5 mile 1961 Denver north From 58th Avenue to Colorado 7 14 miles 1963 Longmont Area From Colorado 7 to Colorado 66 14 miles 1961 North of Denver From Colorado 66 to U.S. 34 14 miles 1963 Fort Collins Area U.S. 34 to (now former) Colorado 68 ( Harmony Road ) 8 miles 1965 Colorado 68 to North of Wellington Harmony Road in Fort Collins to Buckeye Road (at that time, Interstate 25 became continuous from Walsenburg north to Colorado/Wyoming border) 23 miles 1968 North Link From north of Wellington ( Buckeye Road ) to Colorado-Wyoming Border 17 miles October 1964 Miscellaneous Interstate 25 Pictures Westbound Lincoln Avenue reaches its junction with Interstate 25 at Exit 193 in Douglas County, south of Denver. Photo taken 08/27/04. Page Updated July 23, 2005.