Southwest Trail Solutions was formed in 2008 by Mark Flint. At that time Mark was a part-time trails program coordinator for Pima County Natural Resources, Parks & Recreation, a position he held until leaving the county in 2019.

Mark began designing and building trails as a volunteer beginning in the early 1990s4; his first system design was in what is now the Bureau of Land Management Molalla River Recreation area, south of Portland, Oregon. Mark moved to Tucson in 1987, and immediately got involved in trail projects. His first major trail design project in Pima County was in 2004, 35 miles of the Arizona National Scenic Trail between Saguaro National Park and the Santa Rita Mountains in the Coronado National Forest. His volunteer efforts on that project included planning, organizing, fund-raising, and supervising construction of the trail. This project, which took seven years, was done with volunteer labor from community volunteers, who contributed more than 100,000 hours of their time.

Mark designed and built numerous trails and trail parks for the county, including the award-winning Sweetwater Preserve Trails Park.

Beyond the CORE TEAM, STS work includes support from a wide array of cohorts and organizations.