ClearOne (CLRO) had the highest return in August 1990 by a US stock, returning 1,400%.

ASSET	MONTH	% RETURN
ClearOne (CLRO)	August 1990	1,400%
Onto Innovation (ONTO)	August 1990	40%
Aegon NV ADR (AEG)	August 1990	36.38%
Champions Oncology (CSBR)	August 1990	33.33%
US Global Investors (GROW)	August 1990	31.81%
PrimeEnergy (PNRG)	August 1990	28.57%
White Mountains Insurance (WTM)	August 1990	26.12%
SunOpta (STKL)	August 1990	25%
OFG Bancorp (OFG)	August 1990	25%
ACCESS Newswire (ACCS)	August 1990	22.76%
Northrop Grumman (NOC)	August 1990	19.83%
WSFS Financial (WSFS)	August 1990	19.05%
Sabine Royalty Trust (SBR)	August 1990	16.77%
Johnson Controls International (JCI)	August 1990	16.67%
Valero Energy (VLO)	August 1990	16.38%
Destination XL (DXLG)	August 1990	14.29%
Trio-Tech International (TRT)	August 1990	14.28%
Ingles Markets (IMKTA)	August 1990	12.08%
MGP Ingredients (MGPI)	August 1990	11.43%
American Vanguard (AVD)	August 1990	11.36%
BP PLC ADR (BP)	August 1990	10.5%
CSP (CSPI)	August 1990	10%
Avino Silver & Gold Mines (ASM)	August 1990	9.24%
Compass Therapeutics (CMPX)	August 1990	8.7%
Exponent (EXPO)	August 1990	8.63%