Catherine Mary Flanagan was born on August 19, 1888, in Hartford, Connecticut,[1] the second of seven children of Irish immigrant parents.

[2] Her father had moved to the US as a political exile after participating in the Irish Freedom movement, and following his death, she began work as a stenographer and as a bookkeeper at age 13.

[3] In 1917, Flanagan took vacation leave to travel to Washington, D.C., to join the National Woman's Party (NWP) in the Silent Sentinels protest outside the White House.

[2] Flanagan and five other suffragists were arrested on charges of "obstructing traffic and unlawful assembly" and were jailed at the Occoquan Workhouse for 30 days after they refused to pay a $10 fine.

[3] After her release, Flanagan wrote an account of her treatment in jail that was circulated in the national press and attracted public support for the suffrage movement.