Indian Lake State Park centers on Indian Lake, the source of the Great Miami River and a man-made lake created when laborers began the $340,000 Lewistown Reservoir project in the 1850s and completed it in 1860 by turning several small lakes into the second largest man-made lake in the world, second only to Ohio’s Grand Lake St. Marys. The original spillway forming the reservoir was completed in 1860, and after numerous repairs to the aging dam, a new 700-foot labyrinth weir spillway was constructed in 2018 to replace the old dam. The Great Miami River and Indian Lake were instrumental in supplying water to the Miami-Erie Canal, first constructed in 1825 and operated until its abandonment in 1906. Because of its central location on the Toledo and Ohio Central Steamline and the Ohio Electric Railway, Indian Lake became a popular resort area at the turn of the century and was once known as the "Midwest’s Million Dollar Playground." Renamed Indian Lake and established as a public park by the General Assembly in 1898, it remains a popular destination for water-related recreation, with a more than 5,000 acre lake and an 800 acre state park for boating, fishing, swimming, and camping.