Upon returning to Panama, Sprague began painting the country - this included landscapes, fauna, the Canal, but mostly the people. In the 1970's he was the first artist to see the beauty of the national costume and dance of Panama and he began to paint the polleras.
Over the years, Sprague has captured the pride of the traditions and culture of Panama. His work depicts girls adorned in their traditional polleras and montunas, native fishermen, and market vendors.
In addition, Sprague undertook a series of drawings and paintings of the Panama Canal. He produced a total of 29 paintings and drawings for the Panama Canal Company, including depictions the overhaul of two of the sets of Canal locks. Most of the paintings and drawings are on permanent display at the Panama Canal Administration Building in Balboa Heights, Panama.