In 1994, historian and trail buff Ron Kessler called a meeting at the Rio Grande County Museum in Del Norte, Colorado to gauge interest in identifying and preserving remnants of the Old Spanish Trail. It was alert Old Spanish Trail Association (OSTA) members who persuaded Rio Grande County officials to reroute a new access road to a landfill that avoided destroying a section of the Old Spanish Trail's North Branch.

From those humble beginnings, the Old Spanish Trail Association (OSTA) now boasts over 400 members in 27 states with 10 local chapters in six western states and England. The membership is inclusive and involves historians, archaeologists, public land managers, educators, writers, Native Americans, and direct descendants of those who traveled the trail.

From the Southern Ute to federal land managers to Bruce and Rosina Alderson of England, hundreds of members demonstrate a proud passion for the trail for many individual reasons. The Old Spanish National Historic Trail is perhaps like no other for its rich and fascinating history, its past and present day politics, the unique blend of cultural heritages, and the dramatic landscape experienced along this great western trail.

In 2015 the Gerald R. Sherratt Library became the official repository for the Old Spanish Trail Association archive.