LIN TV (LIN) had the highest return in April 1999 by a mega-cap US stock, returning 45%.

ASSET	MONTH	% RETURN
LIN TV (LIN)	April 1999	45.01%
Caterpillar (CAT)	April 1999	36.42%
BHP (BHP)	April 1999	29.49%
Apple (AAPL)	April 1999	27.58%
Wells Fargo (WFC)	April 1999	22.3%
SAP SE ADR (SAP)	April 1999	18.68%
Exxon Mobil (XOM)	April 1999	18.13%
International Business Machines (IBM)	April 1999	17.98%
Chevron (CVX)	April 1999	12.95%
Verizon Communications (VZ)	April 1999	12.85%
Shell PLC ADR (SHEL)	April 1999	12.59%
Coca-Cola (KO)	April 1999	10.9%
American Express (AXP)	April 1999	9.13%
UnitedHealth (UNH)	April 1999	7.16%
Raytheon Technologies (RTX)	April 1999	6.77%
Advanced Micro Devices (AMD)	April 1999	6.02%
Berkshire Hathaway (BRK.A)	April 1999	5.96%
Royal Bank of Canada (RY)	April 1999	4.6%
Johnson & Johnson (JNJ)	April 1999	4.56%
Abbott Laboratories (ABT)	April 1999	4.23%
Berkshire Hathaway (BRK.B)	April 1999	4.13%
Cisco Systems (CSCO)	April 1999	3.22%
Intel (INTC)	April 1999	2.03%
JPMorgan Chase (JPM)	April 1999	2.01%
Mitsubishi UFJ Financial Group Inc ADR (MUFG)	April 1999	1.74%

Mega-cap stocks are treated as having a market cap of $200B+.