Oil Company in Lake Ronkonkoma, NY.

The actual lake, Lake Ronkonkoma, adjacent to the CDP, is the largest lake on Long Island. The land surrounding one side of the lake is in the jurisdiction of the Town of Islip. The elevation of the lake surface is given as 55 feet (17 m) on the most recent USGS map, but as the lake is a “groundwater lake”, not fed by streams, it has no surface outlet and its water surface reflects the current level of the local water table. This can undergo significant changes over time, and the lake level experiences slow periods of rise and fall. In the late 1960s it was quite low; after several intermediate changes in level, in 2007 the lake was higher than at any time since, with a difference of well over 5 feet (1.5 m) between the 1960s low and the 2007 high.

As a result of the lake’s existence, Lake Ronkonkoma was once a resort town, until the area experienced a population explosion in the mid-20th century. Remnants of old resorts and hotels can still be seen around the lake’s shores. Many summer cottages and bungalows from that period remain, now converted to year-round use.

The lake is the subject of a number of urban legends, mainly rooted in the area’s rich Native American heritage. For example: 1. “It’s bottomless” (and/or empties into Long Island Sound or other waterways). In fact, the lake is relatively deep (approx. 65 feet (20 m)) at its southeastern side, and is what’s known as a kettle hole lake. 2. “Every year the lake sacrifices someone.” Or more specifically, Princess Ronkonkoma “The Lady of the Lake” calls young men out to the middle of the lake and drowns them. In all versions, the lady is an Indian princess who herself drowned in the lake, for reasons that vary depending on the story. The most popular version is that every year the lake claims one male victim. Articles suggest that in the past 200 years, only a handful of females have drowned in Lake Ronkonkoma. 3. “There is a mysterious rise and fall of the lake that doesn’t have any noticeable relationship to local rainfall totals.” This has not been sufficiently explained either way.