The Genesee River's name is derived from the Iroquois meaning good valley or pleasant valley. It flows northward through western New York from its source south of the town of Genesee in Pennsylvania and empties into Lake Ontario north of the City of Rochester, New York. The river drains about 2500 mile² (6,500 km²). Falls along the river are within the gorge of Letchworth State Park (the Grand Canyon of the East) near Portageville, New York and within Rochester, where they provided power to 19th century industry. A dam at Mount Morris is the largest flood control dam east of the Mississippi. It has greatly reduced flood damage in the lower Genesee Valley; its capacity has only been exceeded once, during the great flood of 1972, caused by the remnants of Hurricane Agnes. Although the floodwaters went over the spillway, the flooding was partly ameliorated below the dam. The dam was completed in 1952.
Main article: Genesee River: Glacial Geology
The present river valley has been modified extensively from preglacial river valleys. The original river had two branches. The east branch has a larger preglacial valley. It runs south of Mount Morris. It was completely blocked by extensive terminal moraines just south of Dansville, so most of the upper section was diverted toward the Susquehanna River system. Now only a small creek flows in what is left of this large valley. The west branch, which was smaller, is now the Genesee River above Mount Morris.
The River rises in the highlands of the Allegany Plateau in conglomerate, sandstone and shale rocks of Mississippian and Pennsylvanian age, passing through and often exposing older rocks as it drops. At Letchworth it exposes shales, siltstones and some limestones of Devonian age. At Rochester it again cuts a canyon with three more waterfalls in limestones and shales of Silurian age. The river is a highly favored area for fossil collectors, as one can find a great variety over a very long time period within the length of the river.
The Genesee River Valley westward to Lake Erie and the Niagara River was the homeland of the Seneca Nation of the Iroquois Confederacy, also known as The Keepers of the Western Door, as they were the westernmost nation. The Senecas were gradually divested of their homelands and now have just three small reservations left.
The falls at present day Rochester were likely the main reason for the city's existence, as they provided water power for mills. When the Erie Canal opened in 1825 the mills could ship their products cheaply to New York City, and business boomed. Rochester became known as Flour City.
Most of New York west of the Genesee River was part of the Holland Purchase after the American Revolution. From 1801 to 1846 the entire region was sold to individual owners from the Holland Land office in Batavia, New York. Today the region derives its name from the river and is generally referred to as Genesee Country. To the east of the river is the Finger Lakes geographic region.
Following the spectacular success of the Erie Canal, completed in 1825, a group of investors dreamed of connecting the Erie Canal to the Mississippi River System by building a new canal from the Erie, near Rochester, up the Genesee Valley, across to the Allegany River at Olean, thence downward to the Ohio and Mississippi valleys. Construction of the Genesee Valley Canal was begun in 1836, and new sections extended upriver, southward until 1880. During that time the canal was an important commercial route for the valley. The canal was plagued by frequent flood damage and the final leg down the Allegany River was never completed.
The most difficult section to build was the bypass around the gorge and falls at present day Letchworth. The canal followed the old Native American portage route, which necessitated many locks. These old locks can still be seen near Nunda. The project was abandoned and the right of way was sold in 1880. The property became the roadbed for the Genesee Valley Canal Railroad, which eventually merged with the Pennsylvania Railroad.
In 1852 a wooden railroad bridge was built over the Upper Falls at Portageville. It was the largest all wood bridges built at the time. The wood from 300 acres (1.2 km²) of trees was required for its timber.
List of Communities on the Genesee River (north to south)
- Town of Irondequoit
- City of Rochester
- Town of Gates
- Town of Brighton
- Town of Chili
- Town of Henrietta
- Town of Wheatland
- Town of Rush
- Town of Caledonia
- Town of Avon
- Town of York
- Town of Geneseo: Geneseo
- Town of Leicester
- Town of Mount Morris
- Town of Castile
- Town of Portage
- Town of Genesee Falls: Portageville
- Town of Hume
- Town of Granger
- Letchworth State Park
- Mount Morris Dam