The following list contains the most notable road interchanges within the United States divided by each state, which are mainly part of the national Interstate Highway System and are all freeways intersecting with each other at a junction.
Some of the biggest ones are: Kennedy Interchange (I-64/I-65/I-71) in Louisville, Kentucky; the Marquette Interchange (I-94/I-43/I-794) and the $1.8 billion Zoo Interchange both in Milwaukee, Wisconsin; the Pregerson Interchange (I-110/I-105) in Los Angeles; and the Circle Interchange (I-90/I-94/I-290) in Chicago.[1]
The first stack interchange in the world was the Four Level Interchange (renamed the Bill Keene Memorial Interchange), built in Los Angeles, California, and completed in 1949, at the junction of U.S. Route 101 and State Route 110.[3] Since then, the California Department of Transportation (Caltrans) has built at least eight more four-level stacks throughout the state of California, as well as a larger number of three-level stack/cloverleaf hybrids (where the least-used left-turning ramp is built as a cloverleaf-like 270-degree loop).
Despite the construction of interchanges smoothing flow, 11 of the top 30 most congested stretches of highway in the U.S. are in Los Angeles.[4]