For the first time on Thursday, the S&P closed at a record high and the Dow Jones Industrial Average broke above the 24,000 mark.
This as investors gained confidence that the Republican party's push for a U.S. tax overhaul would succeed.
Republican Senator John McCain's decision to back the tax bill provided a new jolt of momentum for the legislation.
McCain had helped defeat Republicans' efforts to repeal Obamacare.
A "yes" vote by him on the tax measure was considered crucial.
Although it is "far from perfect," he said the tax bill would boost the economy.