Interstate 25 in Colorado

In the US state of Colorado, Interstate 25 (I-25) is a major north–south highway. It runs through important cities like Colorado Springs, Denver, Fort Collins, Broomfield, Loveland, and Pueblo. The highway enters the state from the north near Carr and leaves near Starkville.

I-25 is often called by different names along its path. In Denver, it is known as the Valley Highway. In Colorado Springs, it is called the Monument Valley Highway, and in Pueblo, it is named the Pueblo Freeway. Parts of the road also have special dedications, like the Ronald Reagan Highway in El Paso County and the John F. Kennedy Memorial Highway in Pueblo County.

The highway is an important connection for travel and is considered part of the unofficial Pan-American Highway. It replaced older roads like US 87 and most of US 85 to help people move more easily through the state.

Route description

Starting near the border with New Mexico, Interstate 25 enters Colorado close to the Rocky Mountains. It passes through small towns and rural areas, heading north towards Pueblo. Along the way, it runs near lakes and parks, such as the Trinidad Lake and Pueblo Lake.

From Pueblo, the highway continues north, passing close to Colorado Springs and Fort Carson. It goes by important landmarks like the Evergreen Cemetery and Colorado College. The road then moves into Denver, winding around the city center and passing near universities and parks.

Leaving Denver, Interstate 25 heads north through suburbs and farmland. It passes through cities like Thornton and Fort Collins, with Colorado State University nearby. The highway eventually reaches the border with Wyoming, after traveling through open countryside and small towns.

History

Construction

Ancestors and early freeways

Colorado started planning a modern road along the Front Range as early as 1944, before the national Interstate Highway system.

An old road called SH 1, which was not paved, was finished between Denver and Pueblo by 1919. It took about 2.5 hours to travel between Pueblo and Colorado Springs on this road, or 8.5 hours from Pueblo to Denver. This road was later improved with help from the government and became US 85 and US 87 by 1930. It was now made of concrete and the trip between Pueblo and Colorado Springs was reduced to just one hour.

Denver (in 1948) and Pueblo (in 1949) were the first cities to start building multi-lane road sections along what would become I-25. Denver’s section was called the Valley Highway and was finished by 1958. Colorado Springs started building their Monument Valley Freeway in 1955, which was completed by July 1960. Pueblo’s part, the Pueblo Freeway, was done by July 1959.

Interstate completion

When the national Interstate Highway System began, connections started to be built. Wyoming built a link to Cheyenne in 1964, connecting to Colorado’s stretch.

Connecting to New Mexico was harder because the road had to go over Raton Pass, which is very high and changes elevation quickly. Construction began in 1960, and a link to Trinidad was finished by 1963. The Trinidad Segment over Raton Pass was finally done in 1968.

The last part of I-25 in Colorado, connecting Walsenburg and Trinidad, was completed in 1969. Now, there were four lanes of fast, nonstop highway open for 305 miles from New Mexico to Wyoming.

Improvements and expansion

As more people and traffic grew in Colorado during the 1990s and 2000s, major improvements were planned for I-25.

T-REX (Denver)

The first big project was Transportation Expansion (T-REX). It widened nearly 17 miles of I-25 and the I-225 bypass around Denver. It also added new pedestrian and beauty improvements. T-REX also helped expand Denver’s public transportation lines to reach more areas outside Denver.

The T-REX project began in early 2004 and finished in 2006. It cost $1.67 billion, which was less than planned and two years earlier than expected.

COSMIX (Colorado Springs)

Next was Colorado Springs Metro Interstate Expansion (COSMIX). The road through Colorado Springs had grown very busy, going from about 8,500 cars a day in 1960 to 100,000 cars a day by 2005.

COSMIX started in 2005 and finished by the end of December 2007, four days early. It widened the road to three lanes in each direction and rebuilt two main intersections. It was planned to cost $225 million but finally cost $150 million.

COSMIX was the first part of a bigger plan for I-25 improvements. A second phase widened a 12-mile part to six lanes and added extra lanes at busy exits. The Air Force Academy exit was redesigned to have one exit instead of two, with new roundabouts. This work was done by December 2014.

Greenland Wildlife Overpass

In 2025, the biggest wildlife overpass in North America was built over I-25 in Douglas County. It connects 39,000 acres of nature. The overpass is 200 feet wide and 209 feet long.

It is expected that the Greenland Wildlife Overpass will cut down wildlife-vehicle crashes, which happen about once a day during migration seasons, by 90%.

Future

As of October 2020, a seven-mile segment of Interstate 25 through Pueblo was being upgraded. Improvements included widening two bridges, adding noise walls, making curves safer, and adding lanes for cars to speed up or slow down. This $69 million project has finished.

There is much discussion about the future of Interstate 25 in northern Colorado, from Broomfield to Fort Collins. Ideas range from adding toll lanes to expanding the road to six lanes. However, funding and agreement on what to do are limited. Traffic is growing heavily in Weld and Larimer counties, so changes will need to happen soon.

In Colorado Springs, work is happening to extend Powers Boulevard to meet Interstate 25. This will make it easier to bypass the north end of the town and connect Voyager Pkwy to the Interstate. The first phase includes building a new interchange near exit 156, which was completed in summer 2021.

The Gap is an 18-mile stretch of Interstate 25 between Castle Rock and Monument. It is the only four-lane section between Denver and Colorado Springs. Because more people are living there and using the road, traffic has become heavier. Efforts to improve this area are finished, with a cost of $350 million from local and federal sources.

Exit list

Related routes

Auxiliary routes

Main article: Interstate 225

In Colorado, Interstate 25 has one special route called Interstate 225. This route is about 12 miles long and is located near Denver. It starts from the main highway near the Denver Tech Center and ends at Interstate 70 north of Aurora. This route helps travelers avoid traffic in downtown Denver and gives a direct way to get to Denver International Airport from the southern suburbs. It is the only special route for Interstate 25, as there are no others in Wyoming or New Mexico.

Business routes

Main article: Business routes of Interstate 25

Interstate 25 has two special roads that connect small towns to the highway. In Aguilar, Business Spur 25 runs along Lynn Road, and in Walsenburg, Business Loop 25 serves the town. There used to be three more routes in Trinidad, Colorado Springs, and Castle Rock, but they are no longer in use.