Rondout is an unincorporated community in Lake County, Illinois, United States that first formed around a railroad junction.

Illinois Route 176 passes east–west through Rondout, serving as the "main street" of the community, where it is also called "Rockland Road".

People referred to the community around the junction as Sulfur Glen, due to the high amounts of sulphur in the water nearby.

In 1951, Peter Baker & Son Co. moved their asphalt plant from Lake Forest to Rondout, contributing to the development of the area.

[3][4][5] In the first decade of the 20th century, Rondout junction's original grade-level interlocking tower was replaced by a brick structure.

[8][9][10] Several outlaws, including the "Newton Gang" and a corrupt postal inspector, targeted Milwaukee Road's Fast Mail train and successfully carried out a robbery of more than $2 million of cash, jewelry and securities.

All of the conspirators were caught and prosecuted shortly afterwards, all but $100,000 of the stolen goods were recovered, and a historical marker was built to commemorate the event.

[11] As of 2017[update] commuter trains still pass through Rondout on the Milwaukee District / North Line, and they formerly stopped there at the main Rondout Station located on Rockland Road, just south of the junction's split between the Libertyville/Fox Lake, Illinois, branch and the Chicago-Milwaukee main line at the diamond with the EJ&E.