The Obama Presidential Center promises to be a presidential library like no other.

The four-building, 19-acre “working center for citizenship,” set to be built in a public park on the South Side of Chicago, will include a 235-foot-high “museum tower,” a two-story event space, an athletic center, a recording studio, a winter garden, even a sledding hill.

But the center, which will cost an estimated $500 million, will also differ from the complexes built by Barack Obama’s predecessors in another way: It won’t actually be a presidential library.

In a break with precedent, there will be no research library on site, and none of Mr. Obama’s official presidential records. Instead, the Obama Foundation will pay to digitize the roughly 30 million pages of unclassified paper records from the administration so they can be made available online.