What did historian frederick jackson turner mean when he argued for a safety valve

Safety vale theory was the theory about how to deal with unemployment and it gave rise to the homestead act of 1862 in the United States. Due to the rise of immigrants on the east coast, it was argued hypothesized that they should be given lands in the west to relieve unemployment pressure in the East, the framing of new land law would act as a safety valve. This theory stated that if the eastern region is getting full of immigrants they could move to the west until they can't move any further. The employers opposed the giving away free lands to the employers because they anticipated a shortage of employees. Historians are still divided about the success and failure of the homestead act. The Safety valve theory was presented by Fredric Turner.

answer; /// i believe that the correct answer is (divison of labor);

where is the cartoon dude