Because companies and the governments were working to exploit workers, underpay them, and if they protested, kill them in the streets.
Canada
federal employees
There is no minimum limit for union.
Cesar Chavez.
depends of the company you are wirking , if the organization is unionize ??
the need to unionize workers
http://www.ncjrs.gov/App/Publications/abstract.aspx?ID=115536
unionize farm workers, service workers, and public employees.
To get fair and better pay, to get shorter work weeks, to get healthcare, to get pensions, to prevent abuses by management.
They basically claim that it isn't profitable enough to stay in business and shut down.
The Knights of Labor
Eugene V. Debs platform was that workers have the right to unionize. He was a Socialist, and ran for President in 1912. He earned 6% of the vote.