Qualcomm (QCOM) had the highest return in March 1993 by a US stock in the S&P 500 (GSPC), returning 55.5%.

ASSET	MONTH	% RETURN
Qualcomm (QCOM)	March 1993	55.54%
Mohawk Industries (MHK)	March 1993	41.42%
Fair Isaac (FICO)	March 1993	27.12%
Citigroup (C)	March 1993	24.66%
Genesis Healthcare (GEN)	March 1993	22.63%
Analog Devices (ADI)	March 1993	22.39%
Contura Energy (CTRA)	March 1993	21.28%
Regeneron Pharmaceuticals (REGN)	March 1993	19.61%
Electronic Arts (EA)	March 1993	19.39%
Ametek (AME)	March 1993	18.95%
Lowe's Companies (LOW)	March 1993	18.34%
Devon Energy (DVN)	March 1993	17.72%
Kroger (KR)	March 1993	17.69%
Morgan Stanley (MS)	March 1993	17.18%
Omnicom (OMC)	March 1993	16.8%
West Pharmaceutical Services (WST)	March 1993	16.05%
UnitedHealth (UNH)	March 1993	15.81%
Cardinal Health (CAH)	March 1993	15.64%
MGM Resorts International (MGM)	March 1993	15.47%
Williams-Sonoma (WSM)	March 1993	15.24%
Frank's International (FI)	March 1993	14.83%
TJX Companies (TJX)	March 1993	14.53%
STERIS (STE)	March 1993	14.04%
Newmont Goldcorp (NEM)	March 1993	13.92%
Laboratory Corporation of America (LH)	March 1993	13.78%