Applied Materials (AMAT) had the highest return in April 1987 by a large-cap US stock, returning 39.4%.

ASSET	MONTH	% RETURN
Applied Materials (AMAT)	April 1987	39.45%
Adobe Systems (ADBE)	April 1987	34.72%
Western Digital (WDC)	April 1987	26.09%
Teva Pharma Industries Ltd ADR (TEVA)	April 1987	26.06%
Apple (AAPL)	April 1987	25.79%
Lam Research (LRCX)	April 1987	18.63%
Jack Henry & Associates (JKHY)	April 1987	17.69%
Gold Fields Ltd ADR (GFI)	April 1987	16.48%
Telefonaktiebolaget LM Ericsson B ADR (ERIC)	April 1987	16.31%
PACCAR (PCAR)	April 1987	15.33%
Intel (INTC)	April 1987	14.64%
Nucor (NUE)	April 1987	14.54%
Micron Technology (MU)	April 1987	13.69%
Teradyne (TER)	April 1987	12.5%
WW Grainger (GWW)	April 1987	12.5%
Motorola Solutions (MSI)	April 1987	12.21%
Agnico Eagle Mines (AEM)	April 1987	12%
Medtronic (MDT)	April 1987	11%
Kinross Gold (KGC)	April 1987	10.91%
Toyota Motor Corporation ADR (TM)	April 1987	10.47%
Ford Motor (F)	April 1987	9.82%
Analog Devices (ADI)	April 1987	9.68%
Unilever PLC ADR (UL)	April 1987	9.64%
AngloGold Ashanti (AU)	April 1987	8.95%
SEI Investments (SEIC)	April 1987	8.73%

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