1839 Jean Vioget laid out the first plan of Yerba Buena (later San Francisco), showing the Union Square site as a future park.
1847 Jasper O'Farrell created a second, more accurate plan for the blocks of San Francisco, designating this site as a public square. The site was a sand dune called O'Farrell's Mountain.
1850 Colonel John Geary deeded the block to the City to be held in perpetuity for park use.
1860 (circa) The sand dune was removed and the first design for a public square was completed.
1861-1865 The block was named ?Union Square' to commemorate public rallies held here in support of the Union during the Civil War.
1871-1880 The site was cleared and redesigned as a formal strolling garden. Churches and residences surrounded the square.
1877 Cable cars were operating on Powell Street.
1878 Cable cars began running on Geary Street.
1900-1903 Union Square was redesigned with the Dewey Memorial at its center. The memorial was designed by sculptor Robert J. Aitkin and architect Newton J. Tharpe. The ?Winged Victory' bronze figure was modeled after Alma Spreckels, San Francisco socialite, and was named after U.S. Navaal Admiral George Dewey.
1903 The Dewey Memorial was dedicated by President Theodore Roosevelt on May 14.
1905 (circa) By the turn of the century offices, businesses, theaters and hotel surrounded Union Square. The first hotel was the St. Frances located on Powell Street.
1906 The Great Earthquake and Fire destroyed all buildings around Union Square. Temporary hotel rooms were built on the Square while the St. Francis was rebuilt and expanded.
1923 The Fitzhugh Building was built at the corner of Post and Powell Streets where the Saks Fifth Avenue Building stands today.
1928 O'Connor, Moffat & Co. was built at Stockton and O'Farrell Streets where Macy's stands today.
1938 The Union Square Garage Corporation was formed for the purpose of building a garage beneath Union Square.
1941 Construction began on the garage, the first underground parking facility in the world and an air-raid shelter. The architect was Timothy Pfleuger with gardens designed by the City of San Francisco under the aegis of John McClaren, Superintendent of Golden Gate Park.
1942 Mayor Angelo Rossi presided over the dedication ceremonies of the redesigned Union Square and new garage on September 12.
1945 The I. Magnin Building was built on the corner of Geary and Stockton Streets.
1945-1985 Union Square became one of the most popular shopping districts and tourist destinations in the world.
1996 San Francisco Prize held a competition for the redesign of Union Square.
2000 A new design was approved and construction began.
2002 The new Union Square was dedicated by Mayor Willie L. Brown, Jr.