Great Miami River is 163 miles in length, rising in Logan County, Ohio, and flowing south and southwest to the extreme southwest corner of Ohio at the Indiana border. There, the river empties into the Ohio River. The Great Miami starts at 6,700-acre Indian Lake, which was a small natural lake before enlarged in the 1820s to store water for the Miami-Erie Canal. The river passes through seven Ohio counties, including Butler County. The others are Logan, Shelby, Miami, Montgomery, Warren and Hamilton counties. Its major tributaries are the Mad and Stillwater rivers, which join the Great Miami in Dayton, and the Whitewater, which flows from Indiana into the Great Miami near its mouth. The river has average fall of three feet per miles, much greater than the average of six inches per miles for the Ohio River. The lowest point in Butler County (520 feet above sea level) is on the east side of the Great Miami River in Section 25 of Fairfield Township, south of the intersection of River and John Gray roads (see Miami Bottoms). Major floods were in 1805, 1828, 1847, 1866, 1898 and 1913. The latter was the most deadly and destruction. For more information see the Miami Conservancy District and Paper Valley.