The National Park Service has a graduate student internship program that provides a stipend and travel allowance to spend a semester in Washington, DC working with the National Park Service Social Science Program.
Participation is year-round.
The National Park Service also awards dissertation research support as part of its Canon National Parks Service Scholars Program, which provides up to three years of support. Doctoral students in the biological sciences, physical sciences, social sciences, and cultural sciences are eligible. The deadline for application is June 1 of each year.