Interstate 40 (I-40) is an Interstate Highway in Oklahoma that runs 331 miles (533 km) across the state from Texas to Arkansas. West of Oklahoma City, it parallels and replaces old U.S. Highway 66 (US-66), and, east of Oklahoma City, it parallels US-62, US-266, and US-64. I-40 is the longest Interstate highway in Oklahoma. Cities along the route include Erick, Sayre, Elk City, Clinton, Weatherford, Oklahoma City and its suburbs (El Reno, Yukon, Del City, and Midwest City), Shawnee, Okemah, Henryetta, Checotah, and Sallisaw.