Like Pleasureland, Muller's Park was a swim club, picnic, and recreation area that attracted thousands of visitors during the summer months. Muller's and Pleasureland sat back-to-back along the Ramapo River, separated only by a fence. Muller's had similar sized pools, a pavilion, and so on. Muller's Park (then known as the FRG Sports Complex) closed in 1985 after a gang war shootout that killed two people.
This photo from 1999.
See this photo for all the details about Muller's Park's history and the shooting.