Leon Moisseiff was a prominent civil engineer known for his innovative contributions to bridge design in the early 20th century. Born in 1872, he played a significant role in the development of the George Washington Bridge and the Queensboro Bridge in New York City. His work emphasized the importance of using lighter materials and efficient structural designs. Moisseiff is particularly recognized for his development of the "Moisseiff effect," which describes how certain bridge designs can allow for greater flexibility and load distribution. His ideas helped shape modern engineering practices and influenced the construction of many iconic bridges around the world.