Sumner Dam is a dam on the Pecos River in De Baca County in eastern New Mexico. The dam was built by the United States Bureau of Reclamation between 1935 and 1939, a project governed by the Bureau in conjunction with the local Carlsbad Irrigation District. Construction was done by the Bureau with the help of workers of the Works Progress A…Sumner Dam is a dam on the Pecos River in De Baca County in eastern New Mexico. The dam was built by the United States Bureau of Reclamation between 1935 and 1939, a project governed by the Bureau in conjunction with the local Carlsbad Irrigation District. Construction was done by the Bureau with the help of workers of the Works Progress Administration and the Civilian Conservation Corps; some remnants of their artistic rockwork are the five rock bridges on the main road on the east side of the lake.