There are few conferences that could have lured President Obama and three former presidents — Jimmy Carter, Bill Clinton and George W. Bush — as the Civil Rights Summit is doing this week at the LBJ Presidential Library here. This three-day gathering to commemorate the 50th anniversary of the Civil Rights Act, which began on Tuesday, includes Mr. Obama as the keynote speaker on Thursday morning, with the former presidents speaking successively each night. Mr. Carter was to speak Tuesday night; Mr. Bush will conclude the summit on Thursday.

The conference (which is being streamed at civilrightssummit.org) also includes participants from the worlds of academia, politics, media, sports and entertainment, discussing such issues as same-sex marriage, immigration policy, race and sports, women, and education (which the program calls “the ultimate civil right”).

To get another perspective on what is happening here, though, take a look at a temporary display in the Great Hall of this marble library, “Cornerstones of Civil Rights,” which each presidential speaker will be invited to view. A case contains a stovepipe hat worn by President Abraham Lincoln, along with signed copies of the Emancipation Proclamation and the 13th Amendment. In the same case are copies of the Civil Rights Act and the Voting Rights Act of 1965, which were both signed by President Lyndon B. Johnson, along with one of his cowboy hats, a Resistol Golden Beaver.

The juxtaposed hats are meant to have as much significance as the juxtaposed documents, suggesting that the summit’s purpose is not just to examine the legacy of the Civil Rights Act, which President Johnson succeeded in getting passed, against all odds. It is also meant to promote a new assessment of Johnson himself, showing him and Lincoln as kindred spirits.