<Tr> <Th> Time zone </Th> <Td> Eastern: UTC - 5 / - 4 </Td> </Tr> <Tr> <Th> Website </Th> <Td> www.sjcfl.us </Td> </Tr> <P> St. Johns County is a county of the U.S. state of Florida . As of the 2010 United States Census, the county's population was 190,039 . The county seat and largest incorporated city is St. Augustine . St. Johns County is part of the Jacksonville metropolitan area . </P> <P> The county was established in 1821 . It is one of the two original counties established after Florida was ceded to the United States, at the start of the Florida Territorial period, and corresponded roughly with the former colonial province of East Florida . It was named for the St. Johns River, which runs along its western border . </P>

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