Newcastle is situated at the southwest edge of the Black Hills, at the intersection of U.S. routes 16 and 85.

According to the United States Census Bureau, the city has a total area of 2.55 square miles (6.60 km2), all land.

It is named after Newcastle-Upon-Tyne, England, an important coal shipping port.

[8] U.S. Route 85 once ran south from the city to the east of the rail track, crossing them over a five span wide flange steel girder bridge constructed in 1929.

[10][11] The facility was operated by the Wyoming Board of Charities and Reform until that agency was dissolved as a result of a state constitutional amendment passed in November 1990.

[12] The United States Postal Service operates the Newcastle Post Office.

Public education in the city of Newcastle is provided by Weston County School District #1.

[15] The Anna Miller Museum features a model of the ghost mining town of Cambria and the Jenney Stockade Cabin, an old building dating back to the 1874-1879 Black Hills gold rush.

The building was built 1933-1936 as a WPA project as stables for the Wyoming National Guard Cavalry.

34.7% of all households were made up of individuals, and 13.3% had someone living alone who was 65 years of age or older.