The next day after their stay in Alpena they drove to Bay City. Henry said: "In spite of rhe heavy rain we had encountered north of Hillman, there were still columns of smoke at various distances until we reached Bay City". On the 1921 map the route between Alpena and Bay City has two designations: Michigan State Trunkline 10 and Highway 92, the Theodore Roosevelt International Highway. Highway 92 continues past Bay City to Saginaw, Flint, Pontiac, Detroit and then east through Ontario. Trunkline 10 follows the same route but ends in Detroit. Theodore Roosevelt International Highway ran from Portland, Maine to Portland, Oregon. The Michigan portion went from Detroit to Mackinaw City and then from St. Ignace to Ironwood. On their way to Bay City the Pratts would have zigzagged through Spruce, crossed the Au Sable River at Oscoda, (I think it is strange that Henry never mentioned crossing any stream or river they encountered. The bridges must have all been OK). Then they would have passed through the Tawas', Omer, Standish, Pinconning and Kawkawlin. They could have taken the scenic route along Saginaw Bay from Tawas trough Alabaster and Au Gres as US 23 does today but I suspect that on their way home they would have stuck to the main roads. Today that main road route takes you on US 23 to Tawas City, then west on M 55 to M 65, then south on M 65 to US 23 again as far as Standish, then south on M 13 to Bay City. Henry said:"From Bay City we went south and west to St. Johns. On that stretch we had our only car trouble---a flat tire". (remarkable!) "It was getting dark when we reached Kalamazoo. Though only forty miles from home, we stayed overnight". Since he said "...south and west to St. Johns" I am guessing that they went to Kalamazoo via Saginaw, St. Charles, Chesaning, Owosso, Ovid, St. Johns, Lansing, Potterville, Charlotte, maybe Olivet, Bellevue and Battle Creek. The last 40 miles to Watervliet the next day would have taken them through Oshtemo, Paw Paw, Lawrence and Hartford on what the 1921 map calls Highway 84, the Detroit-Chicago Highway.
I have thoroughly enjoyed this exercise. I rank it right up with tracing LaSalle's 1680 walk across the Lower Peninsula and Hugh Heward's 1790 paddle and portage from Lake Erie to Lake Michigan. If anyone got bored with it they probably didn't read this far anyway.