A view of the Portage Park lagoon looking north, around 1917. Portage Park Elementary School can be seen at the right edge of the photo. View Full Caption Northwest Chicago Historical Society

CHICAGO — Nowadays, neighbors flock to Portage Park on sweltering summer days for a dip in one of its two massive swimming pools. But long before the pools were built, swimmers enjoyed a more pastoral setting, as this weekend's #ThrowbackThursday shows.

"Long before air conditioning, Portage Park residents used this lagoon to help relieve the summer heat," according to Frank Suerth, a board member for the Northwest Chicago Historical Society.

The lagoon also used to host swimming competitions for the Pan American Games, according to a 1959 article in the Tribune.

DNAinfo is partnering with the Northwest Chicago Historical Society for a new history post each week. All photos are the property of Northwest Chicago Historical Society unless otherwise indicated.

For more photos and information, visit the Northwest Chicago Historical Society's Facebook page.