St. Petersburg is a city in Pinellas County, Florida, United States. The city is known as a vacation destination for North American and European vacationers, as well as a politically important battleground in U.S. Presidential politics. As of the 2000 census, the city population was 248,232. The 2007 Census stated that the population of St. Petersburg increased to 249,079. The U.S. Geological Survey National Mapping Information locates this city at 27° 46' 14" N 082° 40' 46" W.

That information made St. Petersburg the fourth largest city in the state of Florida and the largest city in Florida that is not a county seat. St. Petersburg is the second largest city in the Tampa Bay Area, which is composed of roughly 4 million residents in the core, making it the second largest Metropolitan Statistical Area in the state.

The city is commonly referred to by locals as "St. Pete"; neighboring St. Pete Beach, Florida formally shortened its name in 1994 after a vote by its residents.

The city is located on a peninsula between Tampa Bay and the Gulf of Mexico. It is connected to the mainland to the north, connected with the city of Tampa, Florida to the east by causeways and bridges across Tampa Bay, and to Bradenton, Florida 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 of 275 into the southern and northern areas of downtown respectively. The Gandy Bridge, conceived by George Gandy and opened in 1924, is 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.

With a purported average of some 360 days of sunshine each year, it is nicknamed "The Sunshine City." For that reason, the city is a popular tourist, and retirement destination, especially for those in the United States from colder Northern climates – particularly New York City, Detroit, and Chicago. However, in recent years the population has shifted in a more youthful direction.

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. Peter Demens won and named the city after his birthplace, while John C. Williams named the first hotel after his birthplace, Detroit (a hotel that was built by Demens). 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.

Philadelphia publisher F. A. Davis turned on St. Petersburg's first electrical service in 1897 and its first trolley service in 1904. The city's first major industry was born in 1899 when Henry W. Hibbs, 1862-1942, a native of Newport, North Carolina, established his wholesale fish business at the end of the railroad pier, which extended out to the shipping channel. Within a year, Hibbs Fish Company was shipping more than a thousand pounds (454 kg) of fish each day.

Dredging of a deeper shipping channel from 1906 to 1908 opened St. Petersburg to larger shipping. Further dredging improved the port facilities through the 1910s. By then the city's population had quadrupled to 4,127.

In 1914, airplane service across Tampa Bay from St. Petersburg to Tampa and back was initiated, generally considered the first commercial airline. The company name was the "St. Petersburg–Tampa Airboat Line" and the pilot was Tony Jannus, flying a Benoist XIV flying boat. The Tony Jannus Award is presented annually for outstanding achievement in the airline industry. Jannus Landing, a local music/entertainment venue on Central Avenue in Downtown, is named after aviation pioneer Tony Jannus.

The city population continued to multiply during the twentieth century. Booming in the 1940's and 50's with the advent of air-conditioning and through the 1970s as the town became a popular retirement destination for Americans from midwestern cities, reaching 238,647 in the 1980 census. By the 1980s, however, the population had levelled off, and has grown by only 10,000 since then, primarily as a result of being "built-out."