Castor is a village in Bienville Parish, Louisiana, United States. The population was 209 at the 2000 census. It was established in 1900. The name "Castor" refers to the genus Castoridae beaver. Castor's Zip Code is 71016 and its telephone numbers start with 544. These numbers are also used by people who live in communities around Castor. These communities include Alberta, Roy, New Ramah, and New Hope; although not all the communities are recognized as townships, they are shown on Bienville Parish maps. People living around Castor but not with-in the City limits often refer to themselves as from Castor, and file information as being from Castor. The Castor Zip Code which bumps against Jamestown, Kepler Lake, and Ashland is a more accurate representation of Castor's actual self-proclaimed population.