It has been represented by Republican Bryant Richardson since his 2014 defeat of Democrat Robert Venables Sr.[3] It is the most Republican-leaning district in the Senate.

District 21 is based in the southwestern corner of Sussex County, including the communities of Seaford, Laurel, Delmar, Bethel, Gumboro, and Reliance.

It overlaps with the 35th, 39th, 40th, and 41st districts of the Delaware House of Representatives.

[1] Delaware Senators are elected to staggered four-year terms.

Under normal circumstances, the 21st district holds elections in midterm years, except immediately after redistricting, when all seats are up for election regardless of usual cycle.