QXO (QXO) had the best month in 2009 by a large-cap US stock in September 2009, returning 550%.

ASSET	MONTH	% RETURN
QXO (QXO)	September 2009	550%
American International (AIG)	August 2009	241.08%
Celsius (CELH)	March 2009	180.02%
Las Vegas Sands (LVS)	April 2009	145.92%
Ford Motor (F)	April 2009	133.61%
Celsius (CELH)	July 2009	129.89%
BitMine Immersion Technologies (BMNR)	April 2009	125%
QXO (QXO)	April 2009	125%
Primo Brands (PRMB)	May 2009	112.27%
Pilgrims Pride (PPC)	April 2009	110.51%
Insmed (INSM)	February 2009	109.09%
Principal Financial (PFG)	April 2009	106.31%
Pilgrims Pride (PPC)	March 2009	104.55%
Owens Corning (OC)	April 2009	101.35%
Tenet Healthcare (THC)	April 2009	99.12%
Freedom (FRHC)	May 2009	97.5%
Smurfit WestRock (SW)	May 2009	97.1%
Wynn Resorts (WYNN)	April 2009	96.15%
Teck Resources Ltd Class B (TECK)	April 2009	95.55%
Dupont De Nemours (DD)	April 2009	93.47%
American International (AIG)	March 2009	92.31%
CBRE Group Inc Class A (CBRE)	April 2009	91.33%
Textron (TXT)	April 2009	90.25%
Bank of America (BAC)	March 2009	89.44%
American Express (AXP)	April 2009	89.06%

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