Answer:In his historic thesis, 'The Significance of the Frontier in American History,' originally presented to a group of fellow historians in Chicago, he argued that as a result of the frontier, American character and society developed differently from European or other known cultures of the time.
Explanation:
Southern Secession is the event or issue that historians can gain.
True, the US Congress was active in implementing labor related legislations. President Theodore Roosevelt gave importance to the labor unions are needed to help on the collective bargaining agreements between employers and employees. The effects of The Great Depression were hard for the workers, it is a call of their duty to act on it.