CREATE TABLE table_53640 ("City" CLOB, "1970" FLOAT, "1980" FLOAT, "1990" FLOAT, "2000" FLOAT, "2010 est." FLOAT)

Which is the lowest 1980 growth that had 2,610 in 1970?
SELECT MIN("1980") FROM table_53640 WHERE "1970" = '2,610'
SELECT MIN("1980") FROM "table_53640" WHERE "1970" = '2,610'