Looks like a possee!!
Or just a 'T' at the rear giving them a head start, need to find the finish photo!
In my opinion, a lot of those cars appear to be Chalmers, especially as indicated by the distinctly down-turned front fenders with squared-off ends and the rear fenders that curve down and then kick straight out.
The Chalmers without front doors would be 1911 and the ones with front doors would be 1912.
Neat picture! I agree with you Erik that several of the cars appear to be Chalmers. I also see an Overland and I believe an EMF.