Nutex Health (NUTX) had the highest return between 2013 and 2015 by a small-cap US stock, returning 29,900%.

ASSET	YEARS	% RETURN
Nutex Health (NUTX)	2013-2015	29,900.01%
Andretti Acquisition Corp II Class A Ordinary Shares (POLE)	2013-2015	896.73%
Prothena (PRTA)	2013-2015	808.13%
Empresa Distribuidora y Comercializadora Norte SA ADR (EDN)	2013-2015	776.5%
Canadian Solar (CSIQ)	2013-2015	727.43%
Gray Television (GTN.A)	2013-2015	651.13%
Pacific Biosciences of California (PACB)	2013-2015	650.29%
MGP Ingredients (MGPI)	2013-2015	622.78%
Gray Television (GTN)	2013-2015	614.89%
BioCryst Pharmaceuticals (BCRX)	2013-2015	549.06%
Old Second Bancorp (OSBC)	2013-2015	527.19%
Universal Insurance (UVE)	2013-2015	491.22%
Xpel (XPEL)	2013-2015	445.14%
Noah (NOAH)	2013-2015	387.95%
Lendingtree (TREE)	2013-2015	383.9%
Independent Bank (IBCP)	2013-2015	348.52%
Novavax (NVAX)	2013-2015	334.72%
Pacira BioSciences (PCRX)	2013-2015	332.38%
JinkoSolar (JKS)	2013-2015	321.8%
Avadel Pharmaceuticals (AVDL)	2013-2015	308.36%
Allient (ALNT)	2013-2015	306.49%
Eyepoint Pharmaceuticals (EYPT)	2013-2015	291.87%
NioCorp Developments Ltd Common Stock (NB)	2013-2015	285.96%
JetBlue Airways (JBLU)	2013-2015	284.55%
Himax Technologies (HIMX)	2013-2015	283.55%

Small-cap stocks are treated as having a market cap between $300M and $2B.