Many of the newcomers beat longtime incumbents by promising to shake things up at City Hall, including 49th Ward Alderman Maria Hadden.
"In order to have real reform in City Council. We need members of City Council to be part of that change," Hadden said.
Lightfoot drove the point home in her inaugural address when talking about bringing integrity back to City Hall. Lightfoot said the days of public officials profiting from office must come to an end.
"Stopping it isn't just in the city's interest, it's in the council's interest," she said.
She paused on that line and turned to the aldermen sitting behind her on stage as the audience applauded loudly.
"Well I just got here, she wasn't talking to me," said 20th Ward Alderman Jeanette Taylor. "She said what she said and I'm OK with that."
"I viewed it as a parent talking to a child, and I think that, like in any relationship, you have to have a conversation and keep that conversation going," said 3rd Ward Alderman Pat Dowell.
There are now 12 Latino members, the most in the council's history. Six of the 12 identify themselves as Democratic Socialists, which makes the City Council lean much more to the left.
They are pushing a very aggressive agenda, which includes raising real-estate transfer tax on the wealthy to pay for the homeless. As Chicago's new mayor, Lightfoot will have to delicately balance their agenda with her own, as well as that of the council's old guard.
Lightfoot has already shaken up the committee structure, by choosing reform alderman Scott Waguespack as her finance chair.
The conversation turned to aldermanic privilege, the longtime practice of giving aldermen power over zoning, licensing and permit decisions in their ward. Lightfoot's first order of business was signing an executive order banning city departments from deferring to aldermen on decisions. Limiting their power is getting mixed reviews from aldermen.
"I don't think the city is ready to see some great City Hall bureaucracy take over yard sales, take over block parties," said 15th Ward Alderman Ray Lopez.
"I've always been opposed to aldermanic prerogative, still do, so I'm excited to see what steps we can make," said 46th Ward Alderman James Cappleman.
Monday was a day of celebration for all City Council members, but especially for the new aldermen taking their oaths for the first time.
"I've been in the council for a long time. I kind of know the personas. We look forward to working with everybody and really making sure that the aldermen are respected and obviously the mayor is respected," said 44th Ward Alderman Tom Tunney.
"First Ward residents are very hopeful particularly when we see the values she's stated around transparency, accountability, equity. These are the values that I lean on, that I was elected on. To have a partner who is interested in turning these into policies, it has shifted the direction of our community. That is something to be very hopeful about," said 1st Ward Alderman Daniel La Spata.
Her first order of business will be about aldermanic prerogative - limiting aldermanic prerogative. Already, that is extremely controversial on the City Council floor.