In 1956 President of the United States Dwight Eisenhower signed the Federal-Aid Highway Act. The act provided for creating 41 thousand-mile “National System of Interstate and Defense Highways” that would reduce hazardous roads, ineffective routes, and traffic jams.

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Since 1956, the Interstate Highway System has become a meaningful way to move people and transport goods, joining cities crosswise the nation. The animated map below shows how the Interstate Highway System grew over the decades.

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Unlike the earlier U.S. Highway System, the Interstates were designed to be an all-freeway system, with nationally unified standards for construction and signage. While some older freeways were adopted into the system, most of the routes were completely new construction, greatly expanding the freeway network in the U.S. Especially in densely populated urban areas, these new freeways were often controversial as their building necessitated the destruction of many older, well-established neighbourhoods; as a result of the many freeway revolts during the 1960s and 1970s, several planned Interstates were abandoned or re-routed to avoid urban cores.

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