557 Area Code – St Louis, Missouri: Location, Time Zone & History

Area code 557 is one of Missouri's newest overlay codes, activated August 12, 2022 across the same territory as area code 314 — the City of St. Louis and its inner-ring St. Louis County suburbs. It arrived only after that territory had already been reshaped twice: area code 573 split away in 1996 to take most of central and southeastern Missouri, and area code 636 split away in 1999 to take the outer St. Louis suburbs, leaving 314 with just the urban core. When even that shrunken footprint neared exhaustion, regulators chose an overlay rather than another geographic split, requiring mandatory 10-digit local dialing from July 15, 2022 ahead of the overlay's activation the following month.

As an overlay, 557 does not carry a distinct city identity of its own — it simply layers new numbers onto the same community served by 314, including St. Louis, St. Charles, Florissant, Chesterfield, Maryland Heights, and Kirkwood. Residents and businesses across that shared territory dial the same way and share the same regional identity regardless of which code their number carries.

The metro economy behind both codes includes biosciences and plant-science research, aerospace and defense work tied to Boeing, brewing associated with Anheuser-Busch, financial services, and healthcare and higher education. The Gateway Arch and the city's blues music heritage remain cultural touchstones common to the whole shared numbering area.