The Battle of the Monocacy, a small but crucial day long conflict, was fought on July 9, 1864. The center of the battle lay at Monocacy Junction, southeast of Frederick, Maryland, on the east bank of the Monocacy along what is now MD Route 355. In spite of repeated attempts by Union troops to burn all bridges over the river, the Confederates persisted and eventually crossed late in the day. Roughly three-quarters of the land in the watershed has been cleared for agriculture and currently supports about 3,500 farms, averaging 150 acres each. The remaining land supports forests, the City of Frederick, and ever-growing residential neighborhoods.
Sediment continues to be a management problem for the basin.
High levels of sediments suspended in surface waters periodically force the closure of drinking water supplies up river and the need for additional chemical treatment in drinking water from lower stretches and the Potomac. Recognizing this, the Maryland Department of Agriculture has targeted the Monocacy watershed as a top water quality management priority. Better erosion control will not only help the river, but farmers, who currently lose an estimated three to seven percent in crop yield in certain areas of the watershed. Of the 3,500 farms in the watershed, most are commercial operations such as dairy, poultry, hogs, and horses. Together, these livestock operations produce nearly 1,119,400 tons of manure annually containing the equivalent of 4,400 tons of nitrogen and 900 tons of phosphorus.