Tens of thousands of people are gathered in Des Plaines, to offer their prayers and promises to Our Lady of Guadalupe.
A candlelight procession kicked off the observance of the Virgin's feast day Thursday night.
The tradition started in Mexico, more than 470 years ago, when an image of the Virgin was said to have appeared several times.
It is an important part of Hispanic faith and culture.
The ‘Our Lady’ shrine is the only place of its kind outside of Mexico City.
120,000 people are expected to make the trip there, as they have done for the past 26 years.
As part of the tradition, pilgrims bring flowers and candles. Many observe the shrine in silence or pray quietly.
Special masses are celebrated every couple of hours, including a midnight mass, led by Chicago’s new archbishop Blase Cupich.