In 1919 – The observation of starlight bending as it passed through the sun’s gravitational field during a total solar eclipse allowed the first experimental test of Albert Einstein’s general theory of relativity. The test was later used to confirm the relativistic effect.
In 1935 – Workers poured the last concrete at the iconic Hoover Dam hydroelectric site. Four months later after the concrete was well and truly set, President Franklin Roosevelt dedicated the dam.
In 1999 – Space Shuttle Discovery completed the first docking with the International Space Station.