A day before the 2022 Leadville 100 mountain bike race, LC&S 1714 idles at the depot between trips. This line's legacy was as a narrow gauge terminus for the Colorado & Southern, but detached past Climax after the 1920s, then converted to a standard gauge line. The line was abandoned by C&S in 1986 after 105 years of continuous service.
LC&S GP9 1714 was built in 1955 as Northern Pacific #241, and has been in place for decades as power for LC&S.
I also believe this is currently the highest elevation operating adhesion (not traction or cog) railroad in the United States (my resources say it's Chama Pass, but this is higher).