Katherine Pollak was born on September 1, 1905, in Yonkers, New York, and grew up in Manhattan in the midst of the Ethical Culture movement.

[1][2] Ellickson started her career in the workers' education movement, teaching and writing for Brookwood Labor College (1929–1932), the Bryn Mawr Summer School for Women Workers in Industry (1927–1949), and the Federal Emergency Relief Administration (FERA) Southern teachers' training school in 1934.

She also did field work in the textile mills of the South and the coal mining camps of West Virginia.

After the merger with the American Federation of Labor (AFL) in 1955, she became assistant director of the AFL–CIO's Social Security Department.

Ellickson recalled in a 1976 interview that as a woman in the labor movement, being middle-class helped her career: early on, she was able to gain valuable experience working in low-paying positions, and later, she could afford to hire help to raise her children and nurse her husband through tuberculosis.