Seneca is an unincorporated community in Montgomery County, Maryland, United States.

Its history goes back before the American Revolutionary War and it thrived when the canal was operating—having several warehouses, mills, a store, a hotel, and a school.

Today (2020), the community uses a Poolesville ZIP code, but is part of the Darnestown census-designated place.

[1] In 1781, the state of Maryland confiscated the lands of Daniel Dulany the Younger, a prominent Loyalist to the Crown from Annapolis.

His land along the Potomac River included a portion along Seneca Creek, and it was sold to help the state pay for the American Revolutionary War.

Robert Peter purchased 2,500 acres (1,000 ha) of the Dulany property in Montgomery County, including the land that contained red sandstone.

He called it Newport, and it was located on the west side of the mouth of Great Seneca Creek, on the Potomac River and about 22 miles (35 km) upriver from Georgetown.

[2] Robert Peter died in 1806, and his eldest son Thomas inherited land near Seneca including the quarry.

[8] In addition to milling operations, Darby's company shipped products on the C&O Canal.

[Note 2] After the war in 1866, the Peter family sold the quarry and nearby property to the newly created Seneca Sandstone Company.

Upton Darby donated land for a one-room schoolhouse that was built using red sandstone from the local quarry.

[13] An 1879 Montgomery County directory lists Seneca as having "public schools and churches in the vicinity".

[18] In this case, the planet was Jupiter, and the discovery led to the growth of a new field of radio astronomy.

A historical marker commemorating the discovery is located on River Road at the management area's parking lot.

[18] All that remains of Seneca are a few homes, the schoolhouse as a museum, the store, and ruins of the stone-cutting mill and quarry.

The southern portion of Seneca Creek State Park is nearby, as is the Bretton Woods Golf Course.

[22] The United States Geological Survey (USGS) lists the community's elevation as 187 feet (57 meters).

[20] Seneca is part of the Darnestown census-designated place (CDP), an unincorporated area in Montgomery County, Maryland.

[35] The nearest general hospital is the Adventist HealthCare Shady Grove Medical Center in Rockville.

[41] Those that live west of Seneca Creek attend Poolesville elementary, middle, and high schools.

[45] Montgomery College has a Germantown campus known as the Pinkney Innovation Complex for Science and Technology.

[54][55] The Seneca Schoolhouse Museum provides tours to schoolchildren so that they can experience a typical school day as it would have been on March 13, 1880.

It is a 1,971 acres (798 ha) tract that provides habitat for deer, turkeys, squirrels, songbirds, and waterfowl.