Interstate 70 (I-70) is an Interstate Highway in the United States that runs from Interstate 15 near Cove Fort, Utah, to a Park and Ride near Baltimore, Maryland. It was the first Interstate Highway project in the United States. I-70 approximately traces the path of U.S. Route 40 (and also the old National Road) east of the Rocky Mountains. West of the Rockies, the route of I-70 was derived from multiple sources. I-70 is the fifth longest Interstate Highway, after I-90, I-80, I-40, and I-10.
The construction of I-70 in Colorado and Utah is considered an engineering marvel as the route passes through the Eisenhower Tunnel, Glenwood Canyon, and the San Rafael Swell. The Eisenhower Tunnel is the highest point along the Interstate Highway system with an elevation of .
The sections of the interstate in Missouri and Kansas have laid claim to be the first interstate in the United States. Though disputed, the Federal Highway Administration has claimed the section of I-70 through Glenwood Canyon, completed in 1992, was the last piece of the Interstate Highway system, as originally planned, to open to traffic.
Interstate 70 begins at an interchange with Interstate 15 near Cove Fort. Heading east, I-70 crosses between the Tushar and Pahvant ranges via Clear Creek Canyon and descends into the Sevier Valley where I-70 serves Richfield, the only town of more than a few hundred people along I-70's path in Utah. Upon leaving the valley near Salina I-70 crosses Salina Summit and then crosses a massive geologic formation called the San Rafael Swell.
Prior to I-70's construction the swell was relatively undiscovered and inaccessible via paved roads. Once this 108 mi (174 km) section was opened to traffic in 1970, it became the longest stretch of Interstate Highway with no services and the first highway in the U.S. built over a completely new route since the Alaska Highway. It also became the longest piece of interstate highway to be opened at one time. Although opened in 1970, this section was not formally complete until 1990 when a second steel arch bridge spanning Eagle Canyon was opened to traffic.
Since I-70's construction the swell has been discovered for its desolate beauty. The swell has since been nominated for National Park and/or National Monument status on multiple occasions. If the swell is granted this status it arguably would be the first time a National Park owes its existence to an Interstate Highway. Most of the exits in this span are view areas, brake check areas, and runaway truck ramps with few traditional freeway exits.
. The traffic signal is controlled from a command center and used for incident management.]] Entering from Utah, I-70 descends into the Grand Valley where it meets the Colorado River, which provides its path up the western slope of the Rocky Mountains. Here I-70 serves the Grand Junction metro area before traversing more mountainous terrain.
The last section of I-70 to be completed was the 15-mile (24 km) Glenwood Canyon. This stretch was completed in 1992 and was an engineering marvel due to the extremely difficult terrain and narrow space in the canyon, which requires corners that are sharper than normal Interstate standards. Construction was delayed for many years due to environmental concerns. The difficulties in building the road in the canyon were compounded by the fact that a railroad occupied the south bank and many temporary construction projects took place to keep U.S. Route 6 open, at the time the only east–west road in the area. Much of the highway is elevated above the Colorado River. The speed limit in this section is 50 mph (80 km/h) due to the limited sight distance and sharp corners. Great care was taken to not destroy the local ecosystem while building the road. An interesting note: all rest areas through this stretch use reclaimed water.
The Eisenhower–Johnson Memorial Tunnel, the highest vehicular tunnel in the world and the longest tunnel built under the Interstate program, passes through the Continental Divide. Because of the Eisenhower-Johnson Tunnel's existence, I-70 is one of few roads connecting ski resorts such as Copper Mountain, Beaver Creek and Vail with Denver and it is more likely to be open than alternative roads. After traversing the mountainous terrain, I-70 goes through Denver and intersects Interstate 25. Leaving Denver, I-70 traverses through wide plains through eastern Colorado before exiting into Kansas.
Bicyclists are permitted to use the shoulder lane of I-70 in portions of Colorado; this is one of the few sections of Interstate Highway where non-motorized vehicles are permitted to use the road.
When leaving the Rocky Mountains, the Denver skyline can be seen on a clear day. This can fool truckers and other unsuspecting drivers because there is still over of steep grade road before reaching the city. A series of signs warn truckers of the steep grade.