Discerning and following the trail of the 19th Ohio (visiting their sites, but not necessarily in exact order) was one of the adventures of my research. Serving from Rich Mountain (W) Virginia to San Antonio Texas, I doubt that there are few regiments that have marched
(and railroads and boats) that far. Some of the interesting stories come from using a regimental history that uses letters, diaries and private journals that describe their adventures on the march. While Google will map the best route today, these journals can fill in the routes they actually marched that, perhaps today, are major US Routes or primary state routes.