Western Maryland's 4-6-6-4's were a dozen fast freight Challengers built by Baldwin in 1940-1941. The railroad's feelings on the engines were mixed and the group was scrapped in the mid-1950s.
The Delaware & Hudson's fleet of forty 4-6-6-4s acquired from Alco in 1940. These steamers operated fast-freights along the D&H system and were fine machines.