There are 20 US Post Offices in Cumberland County serving a total of 185,833 residents equating to 9,292 residents per post office. It's estimated that approximately 296,610 packages are handled across the 20 county post offices annually. Cumberland County is a county located in the U.S. state of New Jersey. The county's Census-estimated population was 155,854 in 2015, representing a 0.7% decrease from the 156,898 enumerated at the 2010 United States Census, in turn increasing by 10,460 (+7.1%) from the 146,438 counted in the 2000 Census, retaining its position as the state's 16th-most populous county. Its county seat is Bridgeton. Cumberland County is named for Prince William, Duke of Cumberland. The county was formally created from portions of Salem County as of January 19, 1748. This county is part of the Vineland-Millville-Bridgeton Primary Metropolitan Statistical Area as well as the Delaware Valley Combined Statistical Area."