Pioneers built homesteads in the Fox River Valley between 1830 and 1860. They were originally attracted to the area that would become Fox River Grove for its beautiful scenery, abundance of clear water and opportunity for hydroelectric power provided by the Fox River.
The Ojibwe people continued to winter in the region into the 1860s.
In 1869, Frank Opatrny purchased of land on the southern shore of the Fox River. The area gained a reputation with city dwellers as a vacation spot. Chicagoans were transported by livery bus from the Illinois & Wisconsin Railroad station in neighboring. In 1900, Frank's son Eman Opatrny bought the land from his father, converting the family land into a tourist destination, the Fox River Picnic Grove which featured several cottages and a restaurant along a stretch of beach on the Fox River. In 1902, Opatrny built the Castle Pavilion, a luxury hotel which incorporated windows from the 1893 World's Columbian Exposition. Opatrny soon after bought approximately 100 additional acres in 1905 and erected several new facilities, including six bars, shooting and photo galleries, and a racetrack.
In 1919, the village of Fox River Grove incorporated becoming the ninth Village in McHenry County. In the same year Louis Cernocky, Sr., established Louis's Place, a restaurant and bar frequented by many prominent Chicago residents. Cernocky added Louis' Crystal Ballroom, located behind the restaurant, in 1922.
In 1931, Theodore Bettendorff began work on what would come to be known as Castle Vianden, which is located along what is now U.S. Route 14. By 1960, the castle, which was open to visitors, had eight towers, a guard room, bugle tower, castle yard, enclosed sun porch, modern kitchen, garage, dungeon, and a wishing well. Bettendorff continued to add to his castle until his death in 1967. During the 1970s, the castle was rented out as a honeymoon retreat. The castle remains a private residence.
In 1942, the Picnic Grove land was purchased by Louis, Jr., and Clara Cernocky. Louis was a successful local businessman and Clara was the daughter of Eman Opatrny. Dubbed "40 Acres of Paradise" by Cernocky, the Picnic Grove remained a popular vacation destination for approximately 20 years before it fell into disarray.
In 1945, Fox River Grove established the first VFW post in McHenry County.
After changing hands several times, in 1994 the Village of Fox River Grove obtained a grant to acquire along the river and named the property Picnic Grove Park. The rest of the land was developed into what is now the Picnic Grove subdivision. Remnants of the Fox River Picnic Grove can still be seen in the park.