CREATE TABLE table_name_2 (district VARCHAR(255), incumbent VARCHAR(255), first_elected VARCHAR(255), result VARCHAR(255))
Which District has a First elected of 1858, and a Result of retired republican gain, and an Incumbent of william millward?
    
SQL: SELECT district FROM table_name_2 WHERE first_elected = 1858 AND result = "retired republican gain" AND incumbent = "william millward"