Many of Post's design's were landmarks of the era. Post's Equitable Life Building (1868–70), was the first office building designed to use elevators; Post himself leased the upper floors when contemporaries predicted they could not be rented. His Western Union Telegraph Building (1872–75) at Dey Street in Lower Manhattan, was the first office building to rise as high as ten stories, a forerunner of skyscrapers to come. When it was erected in "Newspaper Row" facing City Hall Park, Post's twenty-story New York World Building (1889–90) was the tallest building in New York City.