The page, which posts reader-submitted photos of Chicago's past, has nearly 75,000 followers, and most of its content receives hundreds of likes, shares and comments.
"It is really something to realize that there are that many people interested in this topic," said Kaplan, of Jefferson Park. "We are truly proud of our following. People do live everywhere — we have a lot of folks that moved away from Chicago but are still interested in its history, as well as people that are just fascinated by the city's history."
Daniel Pogorzelski, an editor and writer at ForgottenChicago.com and an admin for the Facebook page, said the latter was created as "almost an afterthought," but it quickly took on "a life of its own."
"I would say that the growth of this Facebook group and the success of our website has far surpassed our expectations," said Pogorzelski, of Dunning. "We're so grateful for the dedication of Forgotten Chicago's fans, without whom the group would not be the dynamic forum for seeing Chicago's buildings and structures change and develop over time.
Pogorzelski said Forgotten Chicago's fans come from all over.
"We have all sorts of folks — from devoted locals, former Chicagoans, to people from elsewhere who just visited our city briefly and then became captivated by our intriguing cityscape," he said.
Kaplan said Forgotten Chicago has been great as a connector of Chicago lovers.
The coolest part of the sites, he said, is "getting to know other people around the city who have the same passion for Chicago's history that we do."
Irving Park and Oak Park, 1958. Life Magazine. pic.twitter.com/S5E7q87wkS— Jeff Nichols (@backwards_river) December 5, 2016
Chicago Coliseum, 1916. NARA pic.twitter.com/ZIIRdLJzVv— Jeff Nichols (@backwards_river) December 27, 2016
Biograph, 1951. NARA pic.twitter.com/d1ulVwbvrO— Jeff Nichols (@backwards_river) January 18, 2017