McKinley Park was an open park in the city of Chicago, Earth. The park was characterized by large trees and meadows of green grass.
Miles and Keiko O'Brien once visited McKinley Park. The chief gave his wife a small bracelet during the visit and made Keiko very happy with the present. (TNG: "Power Play")
Noah Lessing had a sister whom he took to McKinley Park when they were children. They watched a family of ground squirrels who lived near a patch of poison ivy. When he was ten, he walked through the poison ivy and swelled up like a Regellian blood worm. He told this story to one of his USS Equinox crewmates in 2376, while passing through a field that resembled the park on a planet in the Delta Quadrant. (VOY: "Equinox, Part II")