Monkey Island is a small island in Grasmere Lake in Washington Park in Denver. It has existed since the man-made lake was dug and filled in 1906. The island, however, wouldn't earn its name until the 1960s when it became a lentic lovers' lane punctuated with recreational drug use common to the era. Locals described it as an island for monkey business and henceforth called it Monkey Island. While the island was once connected to the shore of the lake, the bridge was removed in the 1970s to discourage such behavior. In the 2000s, further visual deterrence was added when the water source for the lake was switched from the Platte River to recycled wastewater. The later source has caused an abundance of algal blooms in the lake surrounding the island due it's high concentrations of nitrogen and phosphorus, whereas historically the Platte River-sourced water left it appearing cleaner. Efforts began in 2011 to improve the lake's overall water quality.