Pamela Bannos says she began researching the history of the area because she was always curious about why there was a tomb in the park, WBBM-AM, Chicago, reported Wednesday.
Bannos found the area used to be the Chicago City Cemetery housing some 35,000 graves.
After the Lincoln assassination, Chicago converted the land to a park and many of the graves were relocated.
However, Bannos found thousands of early Chicagoans remain buried beneath Lincoln Park Zoo. The park district has given her permission to place some markers explaining the park's history.
She's also launching a Web page about her findings at http://hiddentruths.northwestern.edu.