Born in Philadelphia to a Quaker family on June 9, 1865, Helen Marot was schooled at home and raised to be independent. Her father frequently told her, "I want you to think for yourself - not the way I do."

As early as 1893 she took several positions as a librarian in Philadelphia and Wilmington, Del. In 1897 she opened a small library of her own in Philadelphia for "those interested in social and economic problem." The library soon became a gathering place for liberal thinkers.

In 1899, she was hired by the United States Industrial Commission to investigate the custom tailoring trades in Philadelphia. What she discovered about the poor working conditions, especially for women and children, caused her to change from a peaceful librarian to a militant activist. She went to New York City in 1902 to uncover child labor problems there, which resulted in the formation of the New York Child Labor Committee.

During this time she lectured on the benefits of unions to countless members of the garment trade and organized a new union for bookkeepers, stenographers, and accountants. Her research and assertiveness helped persuade the U.S. Supreme Court to uphold the constitutionality of a law limiting working hours for women.

From 1909 to 1910, the League, under Helen's supervision, led the great Shirtwaist Strike in New York. The strike brought attention to the plight of the workers, empowered women, and began an industrial revolution in the garment industry that led to the formation of the International Ladies' Garment Workers'. In 1912, she was part of a commission that investigated the Triangle Shirtwaist Factory Fire. From 1913 on, she devoted herself to writing, primarily about the labor movement.