John Constantine Williams, Sr. (died 1892) was the cofounder of St. Petersburg, Florida, with Captain Peter Demens.
[2][3] Peter Demens (born Pyotr Alexeyevitch Dementyev) was instrumental in bringing the terminus of a railroad to the area in 1888.
[4] Williams transferred part of his land holdings to the Russian exile in return for Demens extending his Orange Belt Railway line from Sanford, Florida, west to Tarpon Springs and then south along the Gulf coast to Williams's settlement.
It was named after Saint Petersburg, Russia, where Peter Demens had spent half of his youth.
A legend says that John C. Williams and Peter Demens flipped a coin to see who would have the honor of naming the city.