Florida has 4,510 islands that are ten acres (4 ha) or larger in area, the second highest number after Alaska. Much of the state is at or near sea level, and is characterized by sedimentary soil. Florida is the flattest state in the country, with the lowest high point of any U.S. state, at just 345 feet (105 meters).. In 2019, St. Petersburg, FL had a population of 265k people with a median age of 43.8 and a median household income of $61,631. Between 2018 and 2019 the population of St. Petersburg, FL grew from 265,100 to 265,358, a 0.0973% increase and its median household income grew from $58,057 to $61,631, a 6.16% increase. "/>How old is st petersburg florida