McCormick became a member of AFSCME Local 471 when she was hired at a nursing home in her hometown. For the next 25 years, McCormick was active in her local, leading negotiating teams, training stewards across District Council 83, graduating from the Penn State Leadership Academy, and mobilizing members to win at the table.
In 2005, McCormick became one of the original organizers hired by AFSCME Council 13. In 2010, she became a staff representative for AFSCME DC 83. McCormick Sue is also a vice president of the Johnstown/Somerset Central Labor Council, a vice president at the Central Pennsylvania Area Labor Federation, and a member of the Pennsylvania Governor’s Occupational Safety and Health Board. In January 2022, she became the director of AFSCME DC 83.