“It is a joy, an honor, and a responsibility to create a place that reflects the optimism and integrity of the President and the First Lady,” firm partners Tod Williams and Billie Tsien said in a joint statement. “This has been a transformative presidency and we will work to make a Center that embodies and expands the Obamas' vision.”

But what and where the library will be, exactly, remain a mystery.

The Barack Obama Foundation is still deliberating between two historic South Side parks designed by Frederick Law Olmsted and Calvert Vaux: Jackson Park—the site of the 1893 World’s Columbian Exposition—and Washington Park—the proposed site of the Olympic stadium during Chicago’s bid to host the 2016 Olympic Games.

Before Chicago was even selected as a venue (New York and Hawaii were also considered), a preservation group called Friends of the Parks threatened to sue if the library were placed on Chicago parkland. (The same group sued the George Lucas Museum of Narrative Art, which announced last week that it was decamping to California.) The group ultimately backed down after Chicago was selected in May. According to the Foundation, a site will be chosen by the end of this year.

The building design itself is also unknown. Foundation chairman Martin Nesbitt said during a press briefing this afternoon that the competition process was “an exploration of chemistry between the architects and President and First Lady.”

Added competition advisor, architecture critic Paul Goldberger, “The real design process begins anew, right now. It’s really a blank slate.”

In August, the Foundation received 144 responses to its initial RFQ. Seven finalists were announced in December, including Renzo Piano Building Workshop, David Adjaye Associates, Snøhetta, Diller Scofidio + Renfro, SHoP, and John Ronan Architects. In recent weeks, rumors flew that there was an even shorter list that included TWBTA, SHoP, Snøhetta, and John Ronan Architects.

“I think [Tod Williams and Billie Tsien] are truly among the greatest architects of our time and among the most thoughtful,” Goldberger said. “If there is anything that characterizes their work, its a combination of dignity, beauty, and understatement. All of those things will be needed in this challenging project.”

Many hope the museum will spark a much-needed renaissance for the South Side of Chicago, long-plagued by crime and oft-neglected by the City; more than 300 people have been murdered in Chicago this year, many in the neighborhoods surrounding the Obama Library sites.

The Library won’t be TWBTA’s first project on the South Side. In 2012 they completed the well-received Reva and David Logan Center for the Arts for the University of Chicago in Hyde Park. In 2013, they received the National Medal of the Arts. Among the firm’s best-known works are the Barnes Foundation in Philadelphia and the now-demolished American Folk Art Museum in New York.

According to Nesbitt, the Foundation hopes to complete the library by 2021.