user: Question: what is the listing date for Nuckolls county?
Columns: ['Name', 'Built', 'Listed', 'Location', 'County']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Adamson Bridge', '1916', '1992-06-29', 'Valentine', 'Cherry']
SQL:

assistant: SELECT "Listed" FROM "Table" WHERE "County" = 'Nuckolls';