The answer is B. Labor unions initiated to act in America throughout colonial America but increased strength in the 1820's and were very prevalent during the post-civil war era, and increased popularity with miners, steel and fabric mill labors in the 1910's. The Unions acceptance and membership weakened in the 1920's after their main approval and association in 1919. Unions chosen back up in 1929 when the economy
started to go bad.
