There are 10 US Post Offices in Washington County serving a total of 123,913 residents equating to 12,391 residents per post office. It's estimated that approximately 197,779 packages are handled across the 10 county post offices annually. Washington County is a county located in the U.S. state of Utah. As of the 2010 census, the population was 138,115, making it the fifth-most populous county in Utah. Its county seat and largest city is St. George. The county was created in 1852 and organized in 1856. It was named for the first President of the United States, George Washington. Washington County experienced the fifth highest job-growth rate in the United States at one point. Washington County comprises the St. George, UT Metropolitan Statistical Area."