user: Question: What year was the structure in Greensboro, North Carolina considered tallest?
Columns: ['Pinnacle height', 'Year', 'Structure type', 'Main use', 'Country', 'Town']
Types: ['text', 'real', 'text', 'text', 'text', 'text']
Sample row: ['m (ft)', 1969.0, 'Guyed mast', 'VHF-UHF transmission', 'U.S.', 'Hemingford, Nebraska']
SQL:

assistant: SELECT "Year" FROM "Table" WHERE "Town" = 'Greensboro, North Carolina';