The production plant in Schiller Park rolled out the production line Monday.
Hostess products disappeared in the fall when the company went bankrupt. A new company has saved the beloved snacks.
New production, marketing and delivery strategies aim to make the company profitable. In addition, the company is now free of debt and union pensions.
Some employees will come back to the plant, although they may not get paid as much as they previously did.
Over the weekend, millions of fans had the chance to buy them at some Walmart stores and other retailers.
Other Hostess favorites, like Suzy Qs, are expected to hit shelves next month.
The new boxes hitting shelves list the cakes as having 270 calories and a weight of 77 grams for two cakes, or 135 calories and 38.5 grams for one cake. Right before it went out of business, the predecessor company had told The Associated Press that Twinkies were 150 calories per cake. Photos of past boxes online also indicate the weight to have been 42.5 grams per cake.
A spokeswoman for Hostess, Hannah Arnold, said in an email Monday that the size change was made in "mid-2012" by the predecessor company. That would mean it happened in the months leading up to its bankruptcy, as the company was trying to keep its head above water financially.
Twinkies' shelf life also increased just before the old company went bankrupt. A 45-day shelf life, up from 26 days, was a separate change and hit shelves Nov. 1, Arnold said. For retailers who request it, the company also said it's freezing Twinkies so stores can stamp their own expiration dates on them.
Twinkies and other snack cakes were purchased by private equity firms Apollo Global Management and Metropoulos & Co. after Hostess Brands said it was closing down in November. The firms are known for fixing up struggling brands.
Hostess has said that Twinkies will remain the same price, at $3.99 for a box of 10. Retailers may charge different prices, however.
The predecessor company had failed to reach a contract agreement with The Bakery, Confectionary, Tobacco Workers and Grain Millers International Union, its second largest union, which noted that its members had already taken pay cuts to keep Hostess afloat.
The bakers union has encouraged the new owners to change their approach and work with its members. It notes that the experience of its members offers "the best chance for long-term success in consistently putting out a quality product."
The Associated Press contributed to this report.