Goodyear Tire & Rubber (GT) had the highest return in 1967 by a mid-cap US stock, returning 33.4%.

ASSET	YEAR	% RETURN
Goodyear Tire & Rubber (GT)	1967	33.43%
Alcoa (AA)	1967	2.71%

Mid-cap stocks are treated as having a market cap between $2B and $10B.