Tides Thoreau Center San Francisco is a thriving 150,000 square foot multi-tenant center, comprised of twelve buildings in the Letterman District of the Presidio. A pioneer in nonprofit centers, the Thoreau campus houses over 75 charitable organizations and social enterprises working for social justice, quality education, international development, cultural conservation, public health, and environmental stewardship, ultimately fulfilling the Presidio’s vision: combining preservation of the park's historic resources with creation of a global center for a sustainable future.