In the heavily Democratic city, the Republican primary drew just over 2,000 votes.
Haley ended up winning all 19 delegates.
The former UN ambassador is seeking more wins on Tuesday, when 15 primaries and caucuses are being held.
Nikki HaleyPhoto by Scott Eisen/Getty Images
Trump has 244 delegates, Haley has 43, and 1,215 are needed to clinch the nomination.
Haley is the first woman to win a Republican primary.
Haley was campaigning in Maine, which is among the states holding its primary on Tuesday.
D.C. has been the bluest of blue areas of the country.
