Civitas Resources (CIVI) had the best month between January 1, 2017 and June 30, 2017 by a mid-cap US stock in January 2017, returning 122.9%.

ASSET	MONTH	% RETURN
Civitas Resources (CIVI)	January 2017	122.86%
Immunitybio (IBRX)	June 2017	107.95%
TG Therapeutics (TGTX)	March 2017	104.39%
Quantum Computing (QUBT)	February 2017	100%
Century Aluminum (CENX)	January 2017	76.4%
Catalyst Pharmaceuticals (CPRX)	March 2017	75.68%
Camtek (CAMT)	May 2017	67.9%
Star Bulk Carriers (SBLK)	January 2017	65.84%
Plug Power (PLUG)	April 2017	63.5%
NexGen Energy (NXE)	January 2017	58.96%
Floor & Decor (FND)	April 2017	54.29%
HUTCHMED DRC (HCM)	March 2017	53.46%
RH (RH)	March 2017	50.1%
Quantum Computing (QUBT)	April 2017	50%
Option Care Health (OPCH)	June 2017	50%
Lantheus (LNTH)	February 2017	49.71%
CleanSpark (CLSK)	April 2017	49.5%
MakeMyTrip (MMYT)	January 2017	49.11%
Appian (APPN)	May 2017	47.08%
Enphase Energy (ENPH)	January 2017	46.08%
PTC Therapeutics (PTCT)	June 2017	45.82%
Applied Digital (APLD)	January 2017	45%
National Beverage (FIZZ)	March 2017	43.76%
Bausch Health Companies (BHC)	June 2017	43.57%
Axsome Therapeutics (AXSM)	June 2017	42.86%

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