From Welco Corners in Bolingbrook to Indian Head Park, I-55 was built on top of much of old US 66. Here, Route 66 passed through what is now Woodridge, Darien, Willowbrook and Burr Ridge—none of which were in existence in 1926 when the route was created and did not come into existence as suburbs until the late 1950s through late 1960s. The stretch from Darien northeast through what is now Countryside and Hodgkins was then part of a large rural farmland collectively known as Lyonsville, as the eastern end of it was located in Lyons Township in Cook County. This section of mainline I-55 is today signed as Historic US 66, though inconsistently so, making it difficult for travelers to follow along the original 1926 path; however, a section of the original highway that now serves as the two-way north frontage road in Darien, Willowbrook and Burr Ridge retains the old Route 66 feel. The original path is slightly difficult to follow here, due to swings north around the I-55 interchanges between Lemont Road and County Line Road, but not impossible, and taking the north frontage road leads travelers past several sites of historic interest, including Cass Cemetery and the former Martin B. Madden mansion known as Castle Eden (now a Carmelite priory) in Darien as well as the International Harvester experimental fields in Burr Ridge (once known as Harvester, Illinois after the plant located there).