Question: Waterford Flat is a historic village in the town of Waterford in Oxford County, a county located in the state of Maine, in which country?

Context paragraphs:
Waterford Covered Bridge: The Waterford Covered Bridge is a Town lattice truss covered bridge spanning LeBoeuf Creek in Waterford Township, Erie County in the U.S. state of Pennsylvania.  The bridge was built in 1875, and is 85 ft in length.  The Waterford Covered Bridge is one of two remaining covered bridges in Erie County, along with the Harrington Covered Bridge.  The bridge is also the only Town lattice truss bridge in the county and one of only 19 in Pennsylvania.  It was documented by the Historic American Buildings Survey in 1936 and was listed on the National Register of Historic Places in 1980.  In 2011, the bridge was closed due to its deteriorating condition.

North Waterford, Maine: North Waterford is a village in the town of Waterford in Oxford County, Maine.

Oxford Hills Comprehensive High School: Oxford Hills Comprehensive High School is a public high school in South Paris, Oxford County, Maine.  Part of Maine School Administrative District 17, the school serves Oxford, South Paris, Norway, West Paris, Waterford, Hebron, Harrison and Otisfield.

The Lake House (Waterford, Maine): The Lake House is an historic tavern located at the Waterford Flat area of Waterford in Maine.  It is an inn and restaurant north of Keoka Lake and near Mount Tire'm.

Keoka Lake: Keoka Lake is a small lake in the town of Waterford, Maine.  It is south of Waterford Flat and northeast of Waterford City (South Waterford).  It is notable for being adjacent to the birthplace of Artemis Ward.  Also known as Thomas Pond, it is approximately 460 acre in size with a maximum depth of fourteen meters (forty-two feet).  It was formed by glaciers retreating and advancing along with Mount Tire'm, an adjacent mountain.

Oxford, Maine: Oxford is a town in Oxford County, Maine, United States.  The population was 4,110 at the 2010 census.  Oxford is home to the Oxford Plains Speedway, the annual Oxford County Fair, and Oxford Casino.  The town includes the village of Welchville.

Waterford Flat, Maine: Waterford Flat is a historic village in the town of Waterford in Oxford County, Maine, United States.  The village has been called by other names in its history, including Sweats Island, Sweet Island, Swetts Island, and Waterford.  It is located north of Keoka Lake (or Thomas Pond).

Maine State Route 118: State Route 118 (abbreviated SR 118) is part of Maine's system of numbered state highways, located in eastern Oxford County.  It is a secondary highway running 13.04 mi between the towns of Waterford and Norway.  Its western terminus in Waterford is at State Route 35 and its eastern terminus in Norway is at State Route 26 and State Route 117.

Waterford Historic District (Waterford, Maine): The Waterford Historic District encompasses the well-preserved historic town center, also known as Waterford Flat, of the rural inland town of Waterford, Maine.  Settled in 1775, the town grew around a site where Kedar Brook empties into Keoka Lake.  The oldest surviving building, the Lake House, dates to 1797, while most of the houses were built before 1850.  Prominent public buildings include a series designed by John Calvin Stevens, including the Knight Library, Wilkins Community Hall, and First Congregational Church.  The district was listed on the National Register of Historic Places in 1980.

Oxford County, Maine: Oxford County is a county located in the state of Maine, in the United States.  As of the 2010 Census, the county had a population of 57,833.  Its county seat is the town of Paris.  The county was formed on March 4, 1805 from northerly portions of York and Cumberland counties.  It borders the Canadian province of Quebec.

Supporting paragraphs: Waterford Flat, Maine Oxford County, Maine
Answer: United States