CREATE TABLE table_18489 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" FLOAT, "Result" CLOB, "Candidates" CLOB)

In what district was incumbent first elected in 1938?
SELECT "District" FROM table_18489 WHERE "First elected" = '1938'
SELECT "District" FROM "table_18489" WHERE "First elected" = '1938'