What is the highest tower in United state of America ?

Willis Tower, formerly named Sears Tower, is a 108-story, 1451-foot (442 m) skyscraper in Chicago, Illinois. At the time of its completion in 1974, it was the tallest/highest building in the world, surpassing the World Trade Center towers in New York. Currently, Willis Tower is the tallest / highest building in the United States and the fifth-tallest

freestanding structure in the world as well as the fifth tallest building in the world to the roof.

Although Sears' naming rights expired in 2003, the building continued to be called Sears Tower for several years. In March 2009 London-based insurance broker Willis Group Holdings, Ltd., agreed to lease a portion of the building and obtained the building's naming rights as part of the agreement. On July 16, 2009, at 10:00 am Central Time, the building was officially renamed Willis Tower.

General information
Location       233 S. Wacker Drive
                  Chicago, Illinois 60606
                  United States
Status         Complete
Constructed     1970-1973
Use Office,     observation, communication

Height
Antenna or spire 1,730 feet (527 m)
Roof              1,451 ft (442 m)

Technical details
Floor count     108
Floor area       4.56 million sq ft (3.81 million sq ft rentable)
                     424,000 m² (354,000 m² rentable)
Elevators        104, with 16 double-decker elevators, made by Westinghouse, modernized by Schindler Group
 

source: wikipedia