Caledonia Mining (CMCL) had the highest return between 1984 and 2003 by a small-cap US stock, returning 148,582.7%.

ASSET	YEARS	% RETURN
Caledonia Mining (CMCL)	1984-2003	148,582.69%
Universal Insurance (UVE)	1984-2003	16,700%
TrustCo Bank (TRST)	1984-2003	7,220.81%
Cohu (COHU)	1984-2003	4,457.96%
Independent Bank (IBCP)	1984-2003	4,298.11%
Great Southern Bancorp (GSBC)	1984-2003	4,295.76%
Westamerica Bancorporation (WABC)	1984-2003	4,176.48%
Tootsie Roll Industries (TR)	1984-2003	3,709.27%
Idaho Strategic Resources (IDR)	1984-2003	3,150%
Cracker Barrel Old Country Store (CBRL)	1984-2003	3,110.36%
United Fire (UFCS)	1984-2003	3,054.63%
World Kinect (WKC)	1984-2003	2,777.22%
Heartland Express (HTLD)	1984-2003	2,728.54%
Hovnanian Enterprises (HOV)	1984-2003	2,673.59%
OFG Bancorp (OFG)	1984-2003	2,521.31%
Kohl's (KSS)	1984-2003	2,468.02%
USANA Health Sciences (USNA)	1984-2003	2,288.39%
Upbound (UPBD)	1984-2003	2,150.01%
Sturm Ruger (RGR)	1984-2003	2,099.19%
Middlesex Water (MSEX)	1984-2003	2,056.21%
Nabors Industries (NBR)	1984-2003	1,975%
Lindsay (LNN)	1984-2003	1,919.55%
Wendy’s (WEN)	1984-2003	1,890.66%
Forward Air (FWRD)	1984-2003	1,766.04%
Dorchester Minerals (DMLP)	1984-2003	1,734.77%

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