She was elected to the Maryland House of Delegates in 1994 and served 12 years, from January 11, 1995 until January 10, 2007. She served as a member of the Ways and Means Committee, for several years as the Ranking Minority Member. As a state legislator, Jean Cryor served on the state's Thornton Education Commission, and twice was the lead sponsor of a successful bill to suspend sales tax on clothing for Back to School Week. Her legislation protecting the Potomac River was argued before the U.S. Supreme Court. She won a reputation as a strong advocate for school funding, the earned income tax credit for low income workers, and for women's rights.

In June 2007, Cryor was elected unanimously by the Montgomery County Council to the Montgomery County Planning Board. At the same time, she also served as a Commissioner on the Maryland-National Capital Park and Planning Commission until her death.

She was honored as Citizen of the Year by the Almanac Newspapers, Legislator of the Year by the Maryland Retailers Association, Businessperson of the Year by the Maryland Businesses for Responsive Government, Building the Bridge to Excellence in Maryland Public Schools by the State Board of Education, Legislator of the Year by the Childhood Brain Tumor Foundation and Registry of Maryland, Maryland's Top 100 Women by The Daily Record (2003 and 2006), the Woman of Achievement Award by the Suburban Maryland Business and Professional Women Association, and the Lifetime Service from the Potomac Chamber of Commerce. She was elected President of the Women Legislators of Maryland (2004-2005).

Although the only Republican state legislator representing Montgomery County, she remained popular among constituents of both parties for her demonstrated independence, commitment to service and to her community. A fearless and indefatigable advocate for women and the disadvantaged, she won a reputation as a consensus builder and very effective legislator.

An example of her courage and independence was her support of a 2005 bill long advocated by the women's rights organizations to create a Pay Equity Commission to study the persistent gender-based wage gap and make recommendations for its remedy. The bill was vetoed by then-Governor Ehrlich. Cryor was the only legislator who dared cross the party line and support the veto override, voting against the governor from her own party. The override was successful and the Pay Equity Commission was established. Its report and recommendations immediately benefitted women and their families that year and will continue for generations to come.