All throughout the 20th century - Many improvments and new bridges were made. Many types of bridges were nearly perfected. The suspension bridge became very popular and famous.
1920-1940 - Many great suspension bridges were built in America.
1923 - The great bridge designer Alexandre Gustave Eiffel died.
1950's - A new type of girder called a box-girder was introduced. The box-girder made longer spanning bridges possible. It allows air to pass harmlessly around the structure.