Sager's works include the Moro Rock Stairway, several structures at Giant Forest Village-Camp Kaweah Historic District (1926-1927) in Sequoia National Park, and the House of the Sun Visitor Center at that Crater Historic District in Haleakala National Park. In the early 1930s, he was also the assistant park architect at Crater Lake National Park. In 1933, he prepared a general plan for the Crater Lake headquarters area. His works at Crater Lake include the Sinnott Memorial Observation Station, Watchman Lookout Station, Comfort Station No. 72, and structures in the Munson Valley and Rim Village Historic Districts.