Gains in shares of Travelers, up 1.3 per cent, and those of Nike, up 0.8 per cent, offset declines in shares of Cisco, down 1.1 per cent, and those of United Technologies, down 0.8 per cent.
The S&P 500 has risen more than 6 per cent since falling to a two-month low in April as investors ditched an array of momentum stocks. So far this year, the index is up 5.2 per cent. In comparison, the Dow is up just 2.1 per cent this year; the Nasdaq is up 2.3 per cent.
In Europe, the Stoxx 600 Index inched higher to close the session at 343.56. Germany's DAX rose 0.07 per cent. France's CAC 40 slipped 0.06 per cent, while the UK's FTSE 100 shed 0.3 per cent.
European Central Bank policy makers meet on Thursday and are widely expected to announce stimulus measures including a reduction of the central bank's key interest rate.
A report released on Wednesday showed gross domestic product in the euro zone grew 0.2 per cent in the first quarter, down from a revised 0.3 per cent increase in the previous three months.
Analysts are concerned about the spectre of deflation in the region. A report earlier this week showed that the pace of inflation fell to 0.5 per cent last month.
"We see a significant risk of a fall below zero," Jennifer McKeown, an economist at Capital Economics in London, referring to the inflation rate, told Bloomberg News. "While the ECB looks set to cut interest rates and announce some lending incentives after its meeting, we think that it will ultimately need to implement a large scale quantitative-easing program to counter the growing risk of deflation."