Meaning of Interstate Highway System

In'terstate High'way Sys"tem

Pronunciation: [key]
  1. a network of U.S. highways connecting the 48 contiguous states and most of the cities with populations above 50,000, begun in the 1950s and estimated to carry about a fifth of the nation's traffic.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.