Wendell, Town of, Located 11 mi SE of Greenfield; Franklin County (US-T121). Settled in 1754, incorporated as a town in 1781. Named in honor of Judge Oliver Wendell (1733-1818) of Boston, town land-owner, who was interested in the advancement of the community (MA-T1/p49).
I don't know about the General Sedgwick Grand Army Post. There was a General John Sedgwick, quite famous, killed during the Civil War. There are monuments to him at various locations, and counties in Kansas and Colorado are named after him. Most likely, this was, too. Possibly the men who started it served in his army corp during the war.