The black population has declined by 181,000, whites have dropped by 53,000 and Latinos grew by 25,000.
A deal is key to avoiding sending the matter to a costly referendum, or worse, the courts.
The backrooms of City Hall were burning until just before 8 p.m. when aldermen working on the city's new ward map called it a night and agreed to get back to negotiations Friday.
"The fairness of the process depends on who's negotiating," said Alderman Willie Cochran, 20th Ward, when asked how fair the process is.
Cochran's ward is one of two African-American wards slated to be turned Hispanic due to the increase in the city's Latino population as reflected in the 2010 census.
Hispanics are to gain a white ward too. Alderman Richard Mell of the 33rd Ward is drawing up the new map as head of the rules committee and is negotiating with leaders of the council's ethnic caucuses.
"He [the mayor] does not want to get involved with this, he's trusting that we can do it. But I can guarantee you one thing: the mayor has shown great leadership in the past," said Cochran.
Mell's map would displace Cochran, 15th Ward Alderman Toni Foulkes and rookie Nicholas Sposato of the 36th Ward.
Sposato was set to meet Boy Scouts in his ward office Thursday evening and had been assured his interests would be protected in the new map. Instead he is losing 80% of his Northwest Side Montclare neighborhood.
"I was born and raised about two blocks from my office here. Got married, bought a house in Galewood, which is one mile south of my house, been there for almost 29 years now. And it's all being taken away from me," Sposato told ABC7.
Currently, 19 of the council's 50 wards are black, 10 are Hispanic, 20 are white and one is Asian.
"African Americans are going to say, look, we fought for over 100 years to get where we are, why should we give up our power. And Latinos are saying, look, we've never been granted out full power, we've been the junior partners at the table, we want to be full partners," said political scientist Dick Simpson.
Forty one of 50 aldermen have to approve the map or the city will have to run a referendum. Communities that don't like the outcome of that could still go to federal court.
The last map was redrawn in 2000 and it went smoothly. But in 1990 a referendum and ensuing litigation cost the city $20 million, something the mayor no doubt does not want to have to spend this time.