One of the longest stock-market booms in history continued its gravity-defying ascent Thursday, with investors cheering the prospect of deep corporate tax cuts and the rollback of government regulations under President Trump.

The Dow Jones industrial average eclipsed yet another milestone, closing Thursday above 24,000 for the first time. And the Standard & Poor’s 500 index logged its 13th straight month of gains, the longest such streak in history.

Stock markets have been going up, more or less without interruption, since March 2009, the end of the acute phase of the global financial crisis. This eight-and-a-half-year bull market is now the second-longest in history, behind only the rally that lasted from 1987 until 2000.

Investors are embracing Mr. Trump’s pro-corporate presidency, marked by the promise of lower taxes, the installation of former industry executives in key government agencies, and the repeal or relaxation of rules and regulations that have made it hard for some big businesses to expand without fear of interference from Washington.