What organization did workers form in the mid-to-late 1800s to improve pay and working conditions

In the late 1800s, many workers got together to organize what we now know as unions. Those Unions were meant to solve their problems related to working conditions. Some of those problems were: low wages and unsafe working conditions, for example. At first, the workers created local unions in single factories. Eventually, those unions used strikes to try compel employers to raise their wages and/or make working conditions safer.