Barack Obama’s Obama Presidential Center, a three-building complex designed by Tod Williams and Billie Tsien on Chicago’s South Side, has made its intention to embrace its neighborhood very clear—specifically Jackson Park and the Midway Plaisance, the historic Frederick Law Olmsted–designed greenways that have hosted, among other things, the 1893 World’s Columbian Exposition, a.k.a. the “White City.” But what the Center hasn’t made as clear is that the complex’s footprint is growing, with its leaders recently proposing an aboveground parking garage that could take up about five acres of the Midway. The library’s concession for eating into this space is a...