The S&P 500 opened at a record-high 2,401 points and the VIX index of implied volatility - known as the Wall Street "fear gauge" - fell to 9.56, the lowest since late 2006.
The S&P 500 and the Nasdaq hit record intraday highs on Monday, while the VIX .VIX , Wall Street's "fear gauge", closed at its lowest level since 1993.
Fading political risk following France's election of centrist candidate Emmanuel Macron over eurosceptic Marine Le Pen, a strong USA results season, and an improving global economy appear to be helping investors sleep better at night, if recent measures of volatility are anything to go by.
The CBOE Volatility Index (VIX) fell more than 8% today to a 24-year low of 9.71.
"It's been here before, but not much lower than this", said Donald Selkin, chief market strategist at Newbridge Securities in NY.
The euro hit a six-month high against the dollar after Macron comfortably defeated far-right nationalist Marine Le Pen who had threatened to take France out of the European Union.
"Trees don't grow to the sky so we need to be realistic about the market", said Eric Aanes, chief executive officer at Titus Wealth Management.
The S&P 500 briefly touched a record high of 2,399.94.
In the 10 sessions through Monday, the S&P 500 (INDEX:.SPX) has moved in the smallest range ever for such a period, according to a CNBC analysis of FactSet data going back to 1980.
Plus, earnings season has been "quite strong", with 14 percent earnings growth and 75 percent of companies beating expectations in the first quarter, she added.
After the bell, auto rental company Hertz Global Holdings reported a deeper-than-expected quarterly loss and its stock slumped 15 percent.
Nasdaq 100 e-minis NQc1 were up 7.5 points, or 0.13 percent, on volume of 18,251 contracts. Coach shares rose 4.8 percent.
Straight Path STRP.A surged more than 16 percent to $187.51 after an unnamed telecommunications company raised its offer to buy the wireless spectrum holder for about $3.1 billion.
Declining issues outnumbered advancers on the NYSE by 1,352 to 1,183.
The large-cap S&P 500 Index (NYSEARCA:SPY) pared losses to finish flat on Monday.
About 6.3 billion shares changed hands on USA exchanges, below the 6.6 billion daily average over the last 20 sessions.