President Lyndon B. Johnson won Washington, D.C. by an overwhelming margin, receiving over 85% of the vote. This was the first presidential election in which the District of Columbia had the right to vote. The District of Columbia has voted Democratic by overwhelming margins every time since this election.
This was one of only two elections where Washington, D.C. wasn't the largest margin for either candidate along with 1972, this time being second to a 74.28% margin for Goldwater in Mississippi.
Results
1964 United States presidential election in the District of Columbia[1]