[1] Sheehan was elected to the Maryland State House of Delegates in 1974, representing the 26th district in Prince George's County.
[2] Sheehan was appointed by Governor Harry Hughes to be Secretary of State of Maryland in 1983, serving a four-year term.
[1] After her career in public service, Sheehan moved to Anne Arundel County, Maryland and remained active in disability issues, becoming president of the Arc of the United States.
She was inducted into the Maryland Women's Hall of Fame in 2002 and was the 2009 Advocate of the Year for the Anne Arundel Disability Commission.
[1][3] Sheehan died of pneumonia complicated by cystic fibrosis on December 19, 2009, at Johns Hopkins Hospital.