CREATE TABLE table_49821 ("Name" TEXT, "Built" TEXT, "Listed" TEXT, "Location" TEXT, "County" TEXT)

In which year did Blount County build a bridge in Cleveland that was listed on 1981-08-20?
SELECT "Built" FROM table_49821 WHERE "County" = 'blount' AND "Listed" = '1981-08-20' AND "Location" = 'cleveland'
SELECT "Built" FROM "table_49821" WHERE "County" = 'blount' AND "Listed" = '1981-08-20' AND "Location" = 'cleveland'