Green Brick Partners (GRBK) had the best month in 2014 by a mid-cap US stock in March 2014, returning 151.7%.

ASSET	MONTH	% RETURN
Green Brick Partners (GRBK)	March 2014	151.73%
Skeena Resources (SKE)	April 2014	123.53%
NexGen Energy (NXE)	February 2014	101.76%
Quantum Computing (QUBT)	May 2014	100%
Celsius (CELH)	March 2014	97.7%
Centrus Energy (LEU)	July 2014	86.56%
Frontline (FRO)	December 2014	83.21%
Aura Minerals Inc Common Shares (AUGO)	February 2014	81.31%
RadNet (RDNT)	April 2014	73.17%
Amicus Therapeutics (FOLD)	August 2014	71.6%
NexGen Energy (NXE)	August 2014	69.64%
POET Technologies (POET)	November 2014	69.44%
Travere Therapeutics (TVTX)	February 2014	68.29%
Uranium Energy (UEC)	May 2014	62.04%
Paycom Software (PAYC)	November 2014	61.34%
Centerra Gold (CGAU)	June 2014	57.42%
PTC Therapeutics (PTCT)	January 2014	55.83%
Green Brick Partners (GRBK)	February 2014	55.61%
Uranium Energy (UEC)	November 2014	54.91%
Plug Power (PLUG)	March 2014	54.35%
TG Therapeutics (TGTX)	January 2014	51.52%
Xenon Pharmaceuticals (XENE)	December 2014	51.34%
Plug Power (PLUG)	February 2014	50.65%
Aya Gold & Silver Inc Common Shares (AYA)	February 2014	50%
SkyWest (SKYW)	October 2014	48.84%

Mid-cap stocks are treated as having a market cap between $2B and $10B.