Immediately upon graduating, in 1896-97, Cromwell was engaged as assistant physician with Dr. Nelson A. Pennoyer at the Pennoyer Sanatorium,
Kenosha, Wisconsin. At this institution, in addition to the Sanatorium practice, Pennoyer and Cromwell had the care of an active practice in the town of Kenosha. She served on the Board of the Associated Charities and Anti-Tuberculosis League at Wheeling, the Salvation Army, and was a member of the Advisory Board during the planning and installation of the city water filtration system in Wheeling. During
World War I, she served as a member of the Ohio County War Chest, and as chair of the War Work Council of the
YWCA. She WAS president and a member of the board of the Children's Home of Woodsdale, WAs first vice president and chair of the finance committee of the Wheeling YWCA, was a member of the Board of Directors and was president in 1912-14 and 1918-20 of the Wheeling Woman's Club, and was first vice president of the General Federation of Women's Clubs of West Virginia. She was an active leader among the
Republican women of the state. She was elector-at-large on the Republican ticket in 1924 and was the first woman honored with the duty of carrying the electoral vote of her state to
Washington, D.C. She was chair of Republican Women of the First Congressional District. She was appointed by
Governor Ephraim F. Morgan to serve on the advisory board of the educational survey. Governor
Howard Mason Gore appointed her a director of the West Virginia Historical Society. In November 1922, she was elected Republican member of the Board of Education of the Triadelphia District for a four year term, being the first woman member of that board. ==Personal life==