The city continued its four-day celebration on Saturday, with Chicago music artist Common performing a concert with the Grant Park Orchestra.
Jennifer Hudson also made a surprise appearance, delighting fans in the packed crowd.
The concert started at 7:30 p.m. at the Jay Pritzker Pavilion. Most reserved spots appeared to be sold out ahead of the show.
Lawn seating for the concert was free, and many fans had lined up to get into the venue well before the show got underway. The event was be capped off with a fireworks display at 8:45 p.m.
Millennium Park opened July 16, 2004. It was built on top of parking garages and commuter rail lines and it's considered the world's largest rooftop garden. Then-Mayor Richard Daley was driving force behind the massive project.
READ MORE | 20 years later, a history of how Millennium Park was transformed into the iconic downtown Chicago venue as we know it today
Millennium Park is part of the iconic imagery that sells Chicago to the world. The lakefront campus in the heart of downtown is home to the iconic Cloud Gate statue also known as The Bean, where people from all over the world come to take pictures.
Millennium Park is filled with interactive fountains, greenspace, tranquil gardens, public art, skating rinks and the Pritzker Pavilion, which hosts free concerts.
In 2015, Millennium Park also became the location of the city's annual Christmas tree lighting.
Two Chicago icons joined together as part of the celebrations Saturday, Eli's Cheesecake and Cloud Gate.
"It's cake imitates art. We have a bean on top!" Eli's Cheesecake President Marc Schulman said.
A birthday celebration would not be complete without cake, and 1,000 slices of cheesecake were handed out to visitors, while the cake itself was donated to Taste to the Homeless. Schulman reminisced about the days when Millennium Park was nothing more than a sunken railyard parking lot.
"We've been doing Taste of Chicago, it's now 44 years," Schulman said. "And we used to park here to go to Taste, and our children were really small."
These days, Millennium Park receives 20 million visitors a year, whether it is to enjoy a free concert at Pritzker Pavilion, hang out at Crown Fountain or simply to take a photo at the Bean.
Among the visitors Saturday were Jerry Fuscone and his wife, who used to live in the area before the reconstruction.
"It's really great that the city has done this," Fuscone said. "We appreciate coming down here as often as we can. It might not be every weekend, but we try to get down here."
Millennium Park's significance is great to visitors and Chicago residents alike.
"It's great for the residents but it draws an international crowd and that's very, very important for a city like Chicago to be on the international map for tourism and it also shows that we care for our city and our continually revitalizing the park, programming it," Eleanor Gorski, Chicago Architecture Center CEO, said.
The Chicago Department of Cultural Affairs operates the public park and is hosting a free four-day millennium park 20th anniversary celebration which runs Thursday through Sunday featuring performances, activities and fireworks.
Thursday night, the celebration kicked off with Sueblo presenting an evening highlighting the musical tapestry of Latin culture on the Jay Pritzker Pavilion stage.
Friday night, the Chicago Symphony Orchestra performed music from "Star Wars" and more.
The free events are all to say "Happy Birthday" to Millennium Park.
List of events:
Thursday
-¡Súbelo! will present an evening highlighting the musical tapestry of Latin culture on the Jay Pritzker Pavilion stage.
-Chuwi, a tropical, indie fusion quartet from Puerto Rico merging salsa, boleros, and folk music with flashes of alternative Hip Hop, psychedelic, and electronic.
-Codigo FN,hailing from Sinaloa, Mexico, this Mexican Regional group debuted with intensity on the Billboard charts.
-Fruko y Sus Tesos with special guest Sonora Dinamita featuring Alfredo de la Fe. Acclaimed Salsa band from Colombia Fruko y Sus Tesos performs as part of their 60th anniversary tour.
Friday, July 19
- Grant Park Orchestra will perform Star Wars and More: the Music of John Williams. Enjoy iconic musical selections- costumes welcome.Saturday, July 20
--A full slate of events, culminating in Chicago native, rapper and actor Common performing with the Grant Park Orchestra, followed by a fireworks display.
-Millennium Park Summer Workouts with Pilates and Yoga
-Family-friendly artmaking with Somos Arte in the North Promenade Tent.
-Chicago Physical Theater Festival performances featuring the Chicago Boyz Acrobatic Team, Alexander D'Amazing, Eric Robinson, and Stephanie Diaz with Gaby Diaz, sharing acrobatic displays, clowning and spectacle, trampoline feats, cicada puppets and more in Wrigley Square.
-Dance performances in the North Promenade Tent
-INT'L CAFE sparks opportunities for cultural exchange by connecting language speakers/signers of all levels for immersive conversations with new friends in the North Promenade Tent.
-Heart of Chicago Soul Club spinning all vinyl, rare and Northern Soul, with Northern Soul Dancing taught by Miss Wolff's Jiving School in the North Promenade Tent.
-Eli's Giant Cheesecake celebrating Millennium Park's 20th Birthday at Cloud Gate. Join the celebration and enjoy free cheesecake.
-A roving performance by Los Pleneros de Don Segundo with horns, vejigantes, cabezudos, and stilt walkers.
-Pop-up Performances by South Shore Drill Team and Ballet Folklorico de Chicago at Cloud Gate.
-Common will perform with the Grant Park Orchestra
-The evening will culminate with a fireworks display to celebrate Millennium Park's 20th Anniversary.
Sunday, July 21
--The final day of 20th anniversary programming brings a full day of family-friendly activities, plus a dynamic evening concert featuring an array of award-winning performers as part of the "The S&S Chicago Experience," curated by Steve "Silk" Hurley and Shannon "Skip" Syas.
-Family-friendly programming in North Promenade Tent, Crown Fountain, and Wrigley Square.
-Story hour for families at Crown Fountain.
-The Golden Horse Ranch Band family square dance for all ages in the North Promenade Tent.
-Interactive Drum Circleand instrument making led by Rhythm Revolution at Crown Fountain.
-Wonder Wagon brings large, colorful puppets to Wrigley Square with opportunities for hands-on interaction.
-Dance performances from Chicago artists in the North Promenade Tent.
-INT'L CAFE sparks opportunities for cultural exchange by connecting language speakers/signers of all levels for immersive conversations with new friends in the North Promenade Tent.
-Sonorama DJ collective with free dance lessons in Salsa and Cumbia and open dance party featuring vintage Latin sounds in the North Promenade Tent.
-The S&S Chicago Experience at the Jay Pritzker Pavilion stage curated by Steve "Silk" Hurley and Shannon "Skip" Syas