Six trumpeter swan cygnets are the first of the endangered birds to hatch at the Lincoln Park Zoo since 2009.
The chicks will eventually be released into the wild as part of a decade-old recovery program.
The zoo has released 35 swans in Iowa.
Sunny Nelson, the curator of birds, said trumpeter swans were nearly extinct a few decades ago.
The cygnets that hatched Wednesday are the first offspring for the zoo's current mates. The male came to Lincoln Park in 2010 and is a first-time dad. The female has hatched more than 30 chicks.
Trumpeter swans are protective parents who construct heavy nests and defend their territory.
The free zoo started in 1868 with the gift of two mute swans.