The Leola, Pennsylvania plant was #3 and was up and running in early 1963. As far as I can tell, the last Shasta to roll off the assembly line was 1974 and possible 1975. Just not sure of the actual date and year of when they closed.
Just wanted to let you know when you told me my Shasta was built in 1974, I couldn't find anything on it that verified the date until i knocked over the door with the mirror on it which had the date 1973 on the back of it. The mirror was probably in a pile of over stock and finally got used and yes it was a bummer that it got broke.