During the rest of the 1960s, I-55 was built in portions throughout Illinois eventually connecting St. Louis to Chicago where it became the fourth direct route between them.
В течение 1960-х годов I-55 был проложен по всему Иллинойсу, связав Сент-Луис и Чикаго и став четвёртой прямой трассой между ними.