Originally known as the Old Spanish Trail, U.S. 90 (Beach Boulevard) straddles the Mississippi Sound coast from Pass Christian east to Ocean Springs as the main east-west arterial through Harrison County. A well traveled route serving both commuters, tourist and local traffic, U.S. 90 varies with 2015 counts of 14,000 vpd at the Bay St. Louis Bridge and 40,000 vpd through Ocean Springs.
While not a fast through route, U.S. 90 nonetheless joins Bay St. Louis with Pass Christian, Long Beach, Gulfport, Keesler AFB, Biloxi and Ocean Springs. All of those cities are generally bypassed by Interstate 10 to the north. The US highway carries four to six lanes overall, with the exception of the swampy stretch angling southwest from Mississippi 607 to Pearlington and St. Tammany Parish, Louisiana.
U.S. 90 provides a scenic drive through Harrison County from Henderson Point off St. Louis Bay to the Biloxi Bay Bridge into Ocean Springs. Spanish style homes, palm trees, and sandy beaches appear along Beach Boulevard through the Pass Christian and Long Beach areas and between U.S. 49 and Interstate 110 in Biloxi. West of Saint Louis Bay, and east of the Biloxi Bay, U.S. 90 travels more inland through older commercial corridors.
Bridges across St. Louis Bay and Biloxi Bay were heavily damaged by Hurricane Katrina, which made landfall on August 29, 2005 at Bay St. Louis. 22 foot storm surges toppled most of the concrete spans of the two low rise draw bridges. Emergency funds were allocated to replace both spans, with a new high level St. Louis Bay Bridge partially opened on May 17, 2007 and the high level Biloxi Bay Bridge opened with two lanes of traffic on November 1, 2007. Both spans now include multi use paths, while U.S. 90 was expanded to six lanes between Biloxi and Ocean Springs.