HNTB Corporation is an American infrastructure design firm that was founded in 1914. The firm has designed many bridges, roadways, airports, and other infrastructure projects throughout the United States. HNTB has worked on many high-profile projects, including the Hoover Dam Bypass, the Tappan Zee Bridge replacement, and the new terminal at Kansas City International Airport. The firm has over 60 offices throughout the United States and employs over 5,000 people.