Suncor Energy (SU) had the highest return in March 1988 by a large-cap US stock, returning 41.4%.

ASSET	MONTH	% RETURN
Suncor Energy (SU)	March 1988	41.43%
Universal Health Services (UHS)	March 1988	32.32%
Monster Beverage (MNST)	March 1988	32.24%
Fair Isaac (FICO)	March 1988	31.57%
Valero Energy (VLO)	March 1988	30%
CACI International (CACI)	March 1988	28.57%
Best Buy (BBY)	March 1988	22.96%
Telefonaktiebolaget LM Ericsson B ADR (ERIC)	March 1988	21.71%
Humana (HUM)	March 1988	20.48%
AngloGold Ashanti (AU)	March 1988	20%
Stifel Financial (SF)	March 1988	18.52%
Devon Energy (DVN)	March 1988	17.64%
Teva Pharma Industries Ltd ADR (TEVA)	March 1988	17.06%
Graco (GGG)	March 1988	16.61%
Carlisle Companies (CSL)	March 1988	16.21%
ConocoPhillips (COP)	March 1988	16.1%
Williams-Sonoma (WSM)	March 1988	15.95%
Heico (HEI)	March 1988	15.91%
Coca-Cola Consolidated (COKE)	March 1988	14.85%
BHP (BHP)	March 1988	14.57%
Honda Motor Co Ltd ADR (HMC)	March 1988	14.37%
Aflac (AFL)	March 1988	14.04%
Coeur Mining (CDE)	March 1988	13.85%
Kinross Gold (KGC)	March 1988	13.16%
Magna International (MGA)	March 1988	13.05%

Large-cap stocks are treated as having a market cap of $10B+.