Insmed (INSM) had the highest return in June 2014 by a large-cap US stock, returning 52.2%.

ASSET	MONTH	% RETURN
Insmed (INSM)	June 2014	52.17%
Coeur Mining (CDE)	June 2014	35%
Vertex Pharmaceuticals (VRTX)	June 2014	31.21%
Ubiquiti Networks (UI)	June 2014	28.42%
Wheaton Precious Metals (WPM)	June 2014	27.9%
Agnico Eagle Mines (AEM)	June 2014	26.74%
Pan American Silver (PAAS)	June 2014	25.1%
Williams Companies (WMB)	June 2014	25.1%
Franco-Nevada (FNV)	June 2014	25.03%
Hecla Mining (HL)	June 2014	25%
Alamos Gold (AGI)	June 2014	23.96%
MACOM Technology Solutions (MTSI)	June 2014	23.11%
QXO (QXO)	June 2014	23.08%
Silicon Motion Technology (SIMO)	June 2014	22.92%
Western Midstream Partners (WES)	June 2014	22.51%
Veeva Systems Inc Class A (VEEV)	June 2014	22.3%
Royal Gold (RGLD)	June 2014	21.81%
Globalstar, Inc Common Stock (GSAT)	June 2014	21.43%
Targa Resources (TRGP)	June 2014	21.34%
Everpure (P)	June 2014	21.3%
Entegris (ENTG)	June 2014	19.15%
ServiceNow (NOW)	June 2014	18.4%
DexCom (DXCM)	June 2014	17.9%
Rambus (RMBS)	June 2014	17.79%
Super Micro Computer (SMCI)	June 2014	17.53%

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