The city is located on a peninsula between Tampa Bay and the Gulf of Mexico. It is connected to mainland Florida to the north; with the city of Tampa to the east by causeways and bridges across Tampa Bay; and to Bradenton in the south by the Sunshine Skyway Bridge (Interstate 275), which traverses the mouth of the bay. It is also served by Interstates 175 and 375, which branch off I-275 into the southern and northern areas of downtown respectively. The Gandy Bridge, conceived by George Gandy and opened in 1924, was the first causeway to be built across Tampa Bay, connecting St. Petersburg and Tampa cities without a circuitous 43-mile (69 km) trip around the Bay through Oldsmar.
    
     The city was co-founded by John C. Williams, formerly of Detroit, Michigan, who purchased the land in 1876, and by Peter Demens, who was instrumental in bringing the terminus of a railroad there in 1888. St. Petersburg was incorporated on February 29, 1892, when it had a population of only some 300 people. It was named after Saint Petersburg, Russia, where Peter Demens had spent half of his youth.

     A local legend says that John C. Williams and Peter Demens flipped a coin to see who would have the honor of naming the city.[5] Peter Demens won and named the city after his birthplace, while John C. Williams named the first hotel after his birthplace, Detroit (a hotel built by Demens[6]). The Detroit Hotel still exists downtown, but has been turned into a condominium. The oldest running hotels are the historic Pier Hotel, built in 1921, formally Hotel Cordova and The Heritage Hotel, built in 1926.