MongoDB (MDB) had the highest return in March 2019 by a large-cap US stock, returning 45.7%.

ASSET	MONTH	% RETURN
MongoDB (MDB)	March 2019	45.65%
Natera (NTRA)	March 2019	29.6%
Carvana (CVNA)	March 2019	28.76%
Trip Group Ltd ADR (TCOM)	March 2019	26.38%
Futu (FUTU)	March 2019	25.47%
Zscaler (ZS)	March 2019	23.38%
Huazhu (HTHT)	March 2019	19.04%
ConAgra Foods (CAG)	March 2019	18.45%
Coca-Cola Consolidated (COKE)	March 2019	16.52%
Chipotle Mexican Grill (CMG)	March 2019	16.43%
ICICI Bank (IBN)	March 2019	15.41%
HDFC Bank Limited ADR (HDB)	March 2019	15.26%
NVIDIA (NVDA)	March 2019	14.91%
AAON (AAON)	March 2019	14.17%
British American Tobacco (BTI)	March 2019	13.24%
EQT (EQT)	March 2019	13.15%
Neurocrine Biosciences (NBIX)	March 2019	12.91%
Pilgrims Pride (PPC)	March 2019	12.75%
Synopsys (SNPS)	March 2019	12.7%
Liberty Media Corporation Series C Liberty Formula One Common Stock (FWONK)	March 2019	12.7%
Tyson Foods (TSN)	March 2019	12.35%
CarMax (KMX)	March 2019	12.22%
Edwards Lifesciences (EW)	March 2019	12.01%
Snap (SNAP)	March 2019	11.76%
Southern Copper (SCCO)	March 2019	11.46%

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