CREATE TABLE table_18368 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" TEXT, "Result" TEXT, "Candidates" TEXT)

What party did the incumbent from the Illinois 1 district belong to?
SELECT "Party" FROM table_18368 WHERE "District" = 'Illinois 1'
SELECT "Party" FROM "table_18368" WHERE "District" = 'Illinois 1'