Berkshire Hathaway (BRK.A) had the highest return in April 1989 by a large-cap US stock, returning 25.8%.

ASSET	MONTH	% RETURN
Berkshire Hathaway (BRK.A)	April 1989	25.75%
Campbell Soup Company Common Stock (CPB)	April 1989	23.49%
Valero Energy (VLO)	April 1989	22.61%
Adobe Systems (ADBE)	April 1989	20.22%
Oracle (ORCL)	April 1989	20.2%
Tyler Technologies (TYL)	April 1989	19.55%
Applied Materials (AMAT)	April 1989	19.38%
Lam Research (LRCX)	April 1989	19.31%
Expeditors International of Washington (EXPD)	April 1989	19.11%
Williams-Sonoma (WSM)	April 1989	17.41%
Devon Energy (DVN)	April 1989	16.67%
Watsco (WSO)	April 1989	16.1%
Watsco (WSO.B)	April 1989	14.98%
West Pharmaceutical Services (WST)	April 1989	14.69%
NiSource (NI)	April 1989	14.5%
Cardinal Health (CAH)	April 1989	14.47%
Tyson Foods (TSN)	April 1989	14.29%
Charles Schwab (SCHW)	April 1989	14.1%
Thermo Fisher Scientific (TMO)	April 1989	13.97%
Analog Devices (ADI)	April 1989	13.26%
Costco Wholesale (COST)	April 1989	13.2%
CMS Energy (CMS)	April 1989	13%
Stryker (SYK)	April 1989	13%
ONEOK (OKE)	April 1989	12.64%
W R Berkley (WRB)	April 1989	12.62%

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