Joaquin Sanchez Sullivan arrived Wednesday, weighing in at 7 pounds, 15 ounces.
"Linda and I have been blessed with a beautiful baby boy," her husband, Jim Sullivan, said in a statement. "Mother and baby are both healthy and happy. Joaquin's arrival is a long-awaited welcome in our lives and we are richer because of it."
Sanchez, 40, is the eighth member of Congress to have a baby while in office. Her pregnancy attracted an unusual amount of attention because Sanchez, who had been married and divorced, was the first to be openly pregnant out of wedlock.
Marsha Catron, a Sanchez aide, said pictures would be available for her constituents soon, the Long Beach Press-Telegram reported.
"Linda was working right up until the last day of her pregnancy," Catron wrote in an e-mail. "I don't know how she did it, but she was in for votes last night. That's some dedication to the district!"