On April 9, 2025, the White House announced a 90-day pause on its sweeping "Liberation Day" tariffs — and markets exploded higher. The S&P 500 surged 9.52%, its biggest single-day gain since October 2008. The Nasdaq ripped 12.16%, its best session since January 2001 and second-best day ever. The Dow added 7.87%. The rally erased roughly $6.6 trillion in losses that had accumulated over the prior two sessions — the largest two-day wipeout in market history — and became an instant case study in how fast sentiment can reverse when policy pivots.

On April 9, 1865, General Robert E. Lee surrendered the Army of Northern Virginia to Ulysses S. Grant at Appomattox Court House in Virginia, effectively ending the American Civil War after four years and roughly 620,000 dead. Grant offered generous terms — Confederate soldiers could keep their horses and go home — setting the tone for reconciliation. The next day, New York markets rallied 2%, railroads surged 10%, and gold dropped 6% on what the New York Times called "the rise of public feeling."

On April 9, 1959, NASA introduced America's first astronauts to the press — seven military test pilots selected from over 500 candidates to ride the Mercury capsule into space. The group included John Glenn, Alan Shepard, and Gus Grissom, who became instant national heroes at the height of the Cold War space race with the Soviet Union. The Mercury program would consume roughly $2.3 billion in today's dollars and laid the industrial foundation for the aerospace complex that still drives defense and tech contracting.

On April 9, 1965, the Houston Astrodome — billed as the "Eighth Wonder of the World" — hosted its first baseball game, an exhibition between the Astros and the New York Yankees before 47,876 fans, with President Lyndon Johnson in attendance. Mickey Mantle hit a towering home run in the sixth inning, but the Astros won 2–1. The $35 million domed stadium was the largest air-conditioned room on earth and proved that enclosed sports venues could work — launching a stadium-building boom that reshaped the economics of professional sports.

On April 9, 1977, Swedish pop group ABBA reached the top of the U.S. Billboard Hot 100 with "Dancing Queen" — their first and only American chart-topper. The song had already hit No. 1 in over a dozen countries and became the signature track of a band that would sell over 385 million records worldwide. ABBA's catalog later fueled the Mamma Mia! franchise, which has grossed over $1 billion across two films and a perpetually running stage musical.