Tom Thwaites was a professor, recreationist, and author perhaps best known for founding the Mid State Trail, the longest hiking trail in Pennsylvania.
Thwaites was born on August 21, 1931, in Madison. Wisconsin. He earned a doctorate in physics from the University of Rochester in 1959, then accepted a faculty position in physics at Penn State, where he taught until his retirement in 1989. For 29 years, he served as a faculty advisor to the Penn State Outing Club, a student organization focused on outdoor recreation trips, with interests in hiking, cross-country skiing, rafting, and mountain biking.
Upon arriving in State College, Thwaites was enamored with the forests of central Pennsylvania, becoming an avid hiker and studying the region’s natural and human history. He scouted, built, and maintained many trails in the region.
In 1969 he founded the Mid State Trail with the intention of building a long-distance backpacking route that visited numerous state forests, state parks, state natural areas, and other recreation spots throughout central Pennsylvania. With help from the Penn State Outing Club, Thwaites led the effort to find a route for the Mid State Trail and build the footpath.
The trail originally reached from Alexandria in Huntingdon County to Pine Creek Gorge in Tioga County. It traverses the southern reaches of Centre County, mostly along the top of Tussey Mountain. The first segment of the trail to be opened was in Rothrock State Forest on Tussey Mountain near Boalsburg. The trail has since been extended in both directions, and it now reaches from Maryland to New York, connecting with hiking trails in both of those states.
Thwaites was a vocal proponent of converting the United States to the metric system. For this reason, the Mid State Trail is described in metric terms in all promotional and informational materials. Trail maps are printed in metric units, and signposts along the trail list distances to points of interest in kilometers. No other significant hiking trail in the United States is presented in this fashion. The official length of the Mid State Trail is 526 kilometers (327 miles), making it the longest hiking trail that is entirely within the borders of Pennsylvania.
Thwaites founded the Mid State Trail Association in 1982, and that group continues to maintain and advocate for the trail. He was also a member of the statewide Keystone Trails Association, serving as vice president and playing a crucial role in expanding the organization from a volunteer hiking club to a structured non-profit.
In the 1990s, along with his longtime friend and fellow trail builder Ralph Seeley, Thwaites participated in the scouting and construction of the Allegheny Front Trail, the longest hiking trail entirely within Centre County. Thwaites and Seeley used their knowledge of ancient Native-American paths to find routes for several segments of the Allegheny Front Trail.
Upon his retirement, Thwaites turned to writing and published three books in the 50 Hikes series for western, central, and eastern Pennsylvania, all of which went through multiple editions. He also wrote regularly for backpacking guidebooks and other works that promoted Pennsylvania’s hiking trails.
The T-Squared Trail, a connector between two major backpacking trails in Clinton and Lycoming counties, was named in honor of Thwaites. In 2003 he was honored with a commemorative plaque in Rothrock State Forest along the first segment of the Mid State Trail to be built. The plaque is in Harris Township, Centre County, and is found on top of Tussey Mountain south of Boalsburg.
Thwaites died in State College at age 83 on December 25, 2014.
Thanks to Barbara Wiemann, Peter Fleszar, and Kevin Busko for their contributions to this article.
Ben Cramer
Sources:
Byers, Ed. “The Mid State Trail – PA’s 2019 Trail of the Year – Traverses the PA Wilds,” Pennsylvania Wilds, April 7, 2019, https://pawilds.com/mid-state-trail-2019-trail-of-the-year/ (Accessed February 8, 2026).
Cramer, Ben. Guide to the Donut Hole Trail. Spring Mills, PA: Scott Adams Enterprises, 2020.
Guide to the Pennsylvania Mid State Trail (11th ed.). Huntingdon, PA: Mid State Trail Association, 2008.
Pacchioli, David. “Go Metric.” Penn State University, February 28, 1995, https://www.psu.edu/news/research/story/go-metric (Accessed February 8, 2026).
“Thomas Turville Thwaites.” Centre Daily Times (obituary), December 30, 2014, https://www.legacy.com/us/obituaries/centredaily/name/thomas-thwaites-obituary?id=8982626 (Accessed February 8, 2026).
First Published: March 9, 2026