Crews have blocked off Oak Park Avenue between Irving Park Road and Forest Preserve Drive to traffic Friday morning.
They originally wanted to start in April. They stopped and brought in ground-penetrating radar and consulted an archeologist as there could be as many as 10,000 bodies buried under what is now Oak Pak Avenue in a six-acre cemetery on the grounds, including more than 2,000 babies buried here as well.
The area was once the grounds of a Cook County poorhouse and later an asylum for the mentally ill.
The road is being redone in conjunction with the new vets center at Oak Park Avenue and Forest Preserve Drive that will serve vets suffering from dementia and Alzheimer's.
The project is expected to take several months.