The 1251 Avenue of the Americas, formerly known as the Exxon Building, is a skyscraper on Sixth Avenue (also known as Avenue of the Americas) in Manhattan, between 49th and 50th Streets. It is owned by Mitsui Fudosan.ContextThe building was part of the later Rockefeller Center expansion (1960s - 1970s) dubbed the "XYZ Buildings". Their plans were first drawn in 1963 by the Rockefeller family's architect, Wallace Harrison, of the architectural firm Harrison and Abramovitz. Their letters correspond to their height. 1251 is the "X" Building as it is the tallest at 750 ft (229 m) and 54 stories, but was the second one completed (1971). The "Y" is the 1221 Avenue of the Americas, which was the first completed (1969) and is the second in height (674 ft and 51 stories). The "Z" Building, the shortest and the youngest, is the 1211 Avenue of the Americas with 45 stories (592 ft). 1251 is the second-tallest building in the whole of Rockefeller Center, after the Comcast Building.Despite being one of the 100 tallest buildings in the United States, 1251 Avenue of the Americas is almost impossible to see from more than just a few blocks away as it is flanked on all sides by buildings over 500 feet tall. The result is that even though 1251 Avenue of the Americas is approximately as tall as the tallest buildings in cities such as Boston or Minneapolis, it has almost no presence on the New York City skyline.