The only building still standing is the small one near the bridge, with the pyramid-shaped roof. That is Fort Halifax, and the entire area beyond the railroad track is now Fort Halifax Park (Winslow ME).

Motor vehicles were probably Norman Woodbury's car dealership inventory (now the VIP store at corner of Bay Street and Halifax Street.

As others have commented, this is modern day Fort Halifax Park, a national historic site. At the time this was home to Holmes-Swift cash & carry groceries (right) and a Texaco station (left). All buildings other than the single fort house have since been demolished, and the area is now a park.