In what district was incumbent first elected in 1938?
CREATE TABLE table_18489 (
    "District" text,
    "Incumbent" text,
    "Party" text,
    "First elected" real,
    "Result" text,
    "Candidates" text
)
SELECT "District" FROM table_18489 WHERE "First elected" = '1938'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: In what district was incumbent first elected in 1938? ### Input: CREATE TABLE table_18489 (
    "District" text,
    "Incumbent" text,
    "Party" text,
    "First elected" real,
    "Result" text,
    "Candidates" text
) ### Response: SELECT "District" FROM table_18489 WHERE "First elected" = '1938'