The area was occupied at the time of English settlement by the Algonquian-speaking historic tribes of the Wicocomico, Chickacoan, and Patawomeck.

The county was created by the Virginia General Assembly in 1648 during a period of rapid population growth and geographic expansion.

[3] The colonial court ordered the Wicocomico and Chickacoan tribes to merge and by 1655, assigned them a reservation of 4,400 acres (18 km2) near Dividing Creek, south of the Great Wicomico River.

[5] By the early 1700s, the Wicocomico tribe was greatly reduced, and English colonists took control of their lands.

Descendants of the last weroance are working to regain recognition as a tribe, the Wicocomico Indian Nation.

[6] Descendants of the Patawomeck achieved tribal recognition from the state of Virginia in February 2010.

Instead, law enforcement is the responsibility of the county Sheriff, a commonwealth constitutional officer elected every four years, with support from the Virginia State Police.

[20] Reedville is a small village in eastern Northumberland County on the western shore of the Chesapeake Bay.

It is named for Captain Elijah W. Reed (1827-1888), who is credited with bringing the menhaden fishing industry, and the tremendous wealth that resulted from it, to Reedville—and to Northumberland County in general.

Omega, with a fleet of large oceangoing fish-harvesting vessels, supported by a number of spotter aircraft, is a major industry in the area and on the Eastern seaboard.

Menhaden, once caught, are cooked in large mass and processed for further use in various applications, including as a protein additive for poultry feed.

Located at the eastern terminus of U.S. Route 360, Reedville is a popular place to begin fishing charters and trips to Tangier Island in the Bay.

The Millionaire's Row of Victorian Era mansions and several watercraft of the Reedville Fishermen's Museum are listed on the National Register of Historic Places.