McDowell served in the State House during the 1941–42 session and then in the State Senate for the 1943–44 and 1945–46 sessions. During those years he was a director of Interstate Milk Producers Cooperative and member of Delaware Farm Bureau from 1941 until 1948. He served as
Secretary of State for Delaware during Governor
Elbert N. Carvel's first term, from 1949 until 1953, and was a member of New Castle County Zoning Commission in 1953 and 1954. meets with members of Congress. Left to right: Representative
Phil M. Landrum (Georgia); Representative
James William Trimble (Arkansas); Representative Harris B. McDowell Jr. (Delaware); President Kennedy; Representative
Carl Elliott (Alabama); Representative
Stanley R. Tupper (Maine). Oval Office, White House, Washington, D.C. McDowell was elected to the U.S. Representatives in 1954, defeating Republican Lillian I. Martin. During this term, he served with the Democratic majority in the 84th Congress. He lost his bid for a second term in 1956 to Republican
Hal Haskell. McDowell then was elected again to the U.S. Representatives in 1958, this time defeating Haskell, and won election three more times, also defeating Republicans James T. McKinstry in 1960, Wilmer F. Williams in 1962, and James H. Snowden in 1964. During these terms, he served with the Democratic majority in the 86th, 87th, 88th, and 89th congresses. Finally, he lost his bid for a sixth term in 1966 to
William Roth, then a Wilmington lawyer. His support of President
Lyndon B. Johnson's war policies may have contributed to his defeat. In all, he served twice, once from January 3, 1955, until January 3, 1957, and again from January 3, 1959, until January 3, 1967, during the administrations of U.S. presidents
Dwight D. Eisenhower,
John F. Kennedy, and Lyndon B. Johnson. McDowell did not sign the 1956
Southern Manifesto, and voted in favor of the
Civil Rights Acts of 1960 and
1964, and the
Voting Rights Act of 1965. During his time in Congress, McDowell had a predominantly liberal voting record. ==Death and legacy==