The Annex was built in honor of Herman Moncus Owner of Elk Drug Store. Hermon Moncus was especially Interested in history and Indian lore. He gather historical and various paraphernalia of the early settlers. He graduated form Denver School of Pharmacy and worked at, and later owed the Elk Drug Store where he housed his collection. After the store closing in 1968 Herman and his wife Bernice helped start the Tucumcari Historical Museum. This Annex house artifacts he collected over the years.