Traer is an unincorporated community in Decatur County, Kansas, United States. A post office was opened in Traer in 1883, and remained in operation until 1971. The town was originally 1 mile west of its present location and was named Connersville, where a post office was established in 1875. When the town was moved in 1883, it was renamed Traer af…Traer is an unincorporated community in Decatur County, Kansas, United States. A post office was opened in Traer in 1883, and remained in operation until 1971. The town was originally 1 mile west of its present location and was named Connersville, where a post office was established in 1875. When the town was moved in 1883, it was renamed Traer after the city of Traer, Iowa.