CHICAGO (CBS) — The Chicago History Museum will open its long-awaited exhibit on gay and lesbian history in Chicago this spring.

The exhibit “Out in Chicago” will open May 21, museum spokeswoman Lauren Dolan confirmed.

The museum says this will be the first time a mainstream urban history museum has ever put on such an exhibit.

The exhibit will show the evolution of how the GLBT communities of Chicago reflect broader changes in the city over the past 150 years. It will explore the stories of individual Chicago residents past and present, the building buildings of homes and families, the evolution of communities, and political action, according to a museum news release.

“We are very aware that the story represents many facets including struggles and setbacks. We tried to find the balance between the positive experiences of these communities and the prejudices they often faced – helping to tell the whole story,” exhibition co-curator Jill Austin said in the release.

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Most stories of GLBT history in Chicago go back only to the 1920s, when gay and lesbian Chicagoans were visible and accepted in the community of Towertown just west of the Magnificent Mile, and German immigrant Henry Gerber began an early, but unsuccessful, campaign for equality by founding the Society for Human Rights.

But the news release says GLBT Chicagoans were active as far back as the 1850s. Curators of the new exhibit found a city ordinance from 1851 that prohibited openly dressing in the clothing of another gender.

“This exhibition is a unique and timely opportunity to interpret our knowledge based on our historical expertise, and making what we know as scholars and researchers available to the public,” exhibition co-curator Jennifer Brier said in a news release.

The exhibition will be open March 26, 2012.

The museum has also been running a series of programs on GLBT history in Chicago since 2004, and will continue its “Out at CHM” programming this year.