Date of closure uncertain. The park opened in 1893? and one source says 'amusements' were added in 1905. I'm going to list 1893 as opening date as the park was opened as 'a recreation area' AND in days of the popularity of Amusement Parks ??

The first amusement area in the park was constructed during the second half of the 1900 decade. It included a theater, bathhouse, merry-go-round, roller coaster, and other rides and concessions. Soon after, a dance pavilion was built about where the Naval Armory is today. In 1922, the Oasis Ballroom was constructed - one of the finest in the nation, one in which most of the name bands would play. Excursion ships made regular runs to Michigan City from Chicago, bringing crowds to Washington Park. The park, the state prison, and Hoosier Slide were the prime attractions for the visitors. The steamships, along with special railroad excursions, brought steady streams of summertime visitors to Michigan City. A local Historical Society publication records that in the season of 1909, ships and trains alone brought 435,650 persons here. That era ended during World War I. Fires wiped out major amusement area facilities. And the tragedy involving the steamship Eastland--which tipped over in the Chicago River as it was about to sail for Michigan City in 1915, drowning 812 persons--had an understandably negative impact on the popularity of the excursion ship business. In future years, some ships - the Theodore Roosevelt, the United States, the North America, and (as recently as the early 1950s) the City of Grand Rapids - made Michigan City a port of call and the excursion business enjoyed a revival in popularity particularly in the late 1920s and 1930s. Michigan City's first zoo was established in 1927.

CREDITS:EXCERPTS: Michigan City Library--Unknown source photocopies