American International (AIG) had the highest return in August 2009 by a large-cap US stock, returning 241.1%.

ASSET	MONTH	% RETURN
American International (AIG)	August 2009	241.09%
Onto Innovation (ONTO)	August 2009	72.12%
Popular (BPOP)	August 2009	65.38%
Sanmina (SANM)	August 2009	64.58%
QXO (QXO)	August 2009	62.5%
Citigroup (C)	August 2009	51.98%
United Airlines (UAL)	August 2009	48.33%
Las Vegas Sands (LVS)	August 2009	46.56%
Hartford Financial Services (HIG)	August 2009	39.25%
Cemex SAB de CV ADR (CX)	August 2009	38.62%
CNA Financial (CNA)	August 2009	35.79%
James Hardie Industries PLC ADR (JHX)	August 2009	35.77%
Regions Financial (RF)	August 2009	35.33%
Williams-Sonoma (WSM)	August 2009	33.68%
Tower Semiconductor (TSEM)	August 2009	32.05%
Incyte (INCY)	August 2009	29.98%
Evercore Partners (EVR)	August 2009	28.04%
Paramount Skydance Corporation Class B Common Stock (PSKY)	August 2009	27.15%
Lennar (LEN.B)	August 2009	26.58%
Lennar (LEN)	August 2009	25.94%
Royal Caribbean Cruises (RCL)	August 2009	24.95%
KKR (KKR)	August 2009	23.39%
Align Technology (ALGN)	August 2009	23.16%
Jones Lang LaSalle (JLL)	August 2009	22.79%
Ternium SA ADR (TX)	August 2009	21.92%

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