Based on the apparent age of the one-legged man on crutches at 2:20, it is probable he is a Civil War amputee.
It's possible, but he would have been in his sixties when the film was taken. The war had been over for forty six years in 1911.
If you didn't turn off YouTube at the end of the video, it autoplays a couple more items. The first is grainy short scenes from 1895 to 1900. The second is colorized photos of the era.
In one of those colorized photos, some urchins are sitting around an old man with a long beard... and a union Civil War cap with a "139" on it... probably his regiment.
Quite possible. But bear in mind that amputations were much more common back then and people lost limbs as a result of all manner of accidents. Until the early 1900’s there was basically no work place safety laws. It was estimated that in 1890 one in every eleven workers in steel foundries ended up being killed or crippled on the job. The owners didn’t care. Labor was cheap (11 cents per hour on average) and there was no shortage of people waiting for work given the choice of starving.