Where is St Petersburg located and why is it located there?

It is in Florida and is on a peninsula between Tampa Bay and the Gulf of Mexico. It is a popular Tourist and Retirement location because of it's nickname of the "Sunshine City" because it supposedly has 360 days of sunshine per year.

There's also a St. Petersburg in Russia. It was founded in 1703 and was named after St. Peter, not Peter the Great. It's known as "the Capital of the north", and "the Venice of the north".