Amkor Technology (AMKR) had the highest return in July 1999 by a large-cap US stock, returning 52.8%.

ASSET	MONTH	% RETURN
Amkor Technology (AMKR)	July 1999	52.79%
Micron Technology (MU)	July 1999	50.76%
United Therapeutics (UTHR)	July 1999	49.49%
Gilead Sciences (GILD)	July 1999	48.33%
Infosys Ltd ADR (INFY)	July 1999	38.54%
Leonardo DRS, Inc Common Stock (DRS)	July 1999	33.33%
Biogen (BIIB)	July 1999	29.36%
Old Dominion Freight Line (ODFL)	July 1999	29.01%
Check Point Software Technologies (CHKP)	July 1999	27.33%
MasTec (MTZ)	July 1999	27.23%
Amgen (AMGN)	July 1999	26.54%
Coherent (COHR)	July 1999	26.31%
Monster Beverage (MNST)	July 1999	24.72%
Tower Semiconductor (TSEM)	July 1999	24.62%
Cheniere Energy (LNG)	July 1999	23.13%
Gildan Activewear (GIL)	July 1999	22.77%
Zebra Technologies (ZBRA)	July 1999	21.92%
Mettler-Toledo International (MTD)	July 1999	21.52%
Apple (AAPL)	July 1999	20.24%
Fresenius Medical Care (FMS)	July 1999	19.38%
Lam Research (LRCX)	July 1999	18.45%
Laboratory Corporation of America (LH)	July 1999	18.18%
Genesis Healthcare (GEN)	July 1999	17.76%
Intel (INTC)	July 1999	15.48%
Steel Dynamics (STLD)	July 1999	15.45%

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