US investors powered the S&P 500 to an all-time high Thursday, one day after Washington politicians reached a deal to reopen the government and avert a feared debt default. The S&P 500, the broadest of the major measures of US markets, was at 1,733.15 at the closing bell, up 0.67 percent for the day and more than seven points above the previous record closing high of 1,725.52, reached on September 18.