It was the scariest day on Wall Street in years. Stocks went into free fall on Monday, and the Dow plunged almost 1,600 points — easily the biggest point decline in history during a trading day. Buyers charged back in and limited the damage, but at the closing bell the Dow was still down 1,175 points, by far its worst closing point decline on record. The drop amounted to 4.6% — the biggest decline since August 2011, during the European debt crisis. But it was nowhere close to the destruction on Black Monday in 1987 or the financial crisis of 2008. Still, for investors lulled to sleep by the steady upward climb since Election Day, it was alarming.