Niagara River in the context of "Niagara Falls, Ontario"

Lake Ontario (French: Lac Ontario) is one of the five Great Lakes of North America. It is bounded on the north, west, and southwest by the Canadian province of Ontario, and on the south and east by the U.S. state of New York. The Canada–United States border spans the centre of the lake. On the Canadian side, the major cities are Kingston, Mississauga, Toronto, Hamilton, and St. Catharines. On the American side, the major cities are Rochester and Watertown.

The last in the Great Lakes chain, Lake Ontario serves as the outlet to the Atlantic Ocean via the Saint Lawrence River, comprising the western end of the Saint Lawrence Seaway. Its primary inlet is the Niagara River from Lake Erie. The Long Sault control dam, primarily along with the Moses-Saunders Power Dam regulates the water level of the lake.

Buffalo is a city in the U.S. state of New York. It lies in Western New York at the eastern end of Lake Erie and at the head of the Niagara River on the Canada–United States border. It is the second-most populous city in New York, with a population of 278,349 at the 2020 census. The Buffalo–Niagara Falls metropolitan area, with over 1.16 million residents, is the 51st-largest metropolitan area in the United States. Buffalo is the county seat of Erie County.

Before the 17th century, the region was inhabited by nomadic Paleo-Indians who were succeeded by the Neutral, Erie, and Iroquois nations. In the early 17th century, the French began to explore the region. In the 18th century, Iroquois land surrounding Buffalo Creek was ceded through the Holland Land Purchase, and a small village was established at its headwaters. Buffalo was selected as the terminus of the Erie Canal in 1825, which led to its incorporation in 1832 and stimulated its growth as the primary inland port between the Great Lakes and Atlantic Ocean. Transshipment made Buffalo the world's largest grain port in that era. After the coming of railroads greatly reduced the canal's importance, the city became the second-largest railway hub (after Chicago), and the city came to be dominated by steel production by the 20th century. Later, deindustrialization and the opening of the St. Lawrence Seaway saw the city's economy decline and diversify. It developed its service industries, such as health care, retail, tourism, logistics, and education, while retaining some manufacturing.

The geography of New York varies widely across the state. Most of New York is dominated by farms, forests, rivers, mountains, and lakes. New York's Adirondack Park is larger than any U.S. National Park in the contiguous United States. Niagara Falls, on the Niagara River as it flows from Lake Erie to Lake Ontario, is a popular attraction. The Hudson River begins near Lake Tear of the Clouds and flows south through the eastern part of the state without draining lakes George or Champlain. Lake George empties at its north end into Lake Champlain, whose northern end extends into Canada, where it drains into the Richelieu River and then the St. Lawrence. Four of New York City's five boroughs are on the three islands at the mouth of the Hudson River: Manhattan Island, Staten Island, and Brooklyn and Queens on Long Island.

"Upstate" is a common term for New York counties north of suburban Westchester, Rockland and Dutchess counties. Upstate New York typically includes the Catskill Mountains or areas North of the Catskill Mountains, the Capital District, The Adirondacks, the Erie Canal, Lake Champlain, Otsego Lake, Oneida Lake; rivers such as the Delaware, Genesee, Mohawk, and Susquehanna. The highest elevation in New York is Mount Marcy of the Adirondack Mountains. New York is the 27th-largest state.

The moment of inertia, otherwise known as the mass moment of inertia, angular/rotational mass, second moment of mass, or most accurately, rotational inertia, of a rigid body is defined relatively to a rotational axis. It is the ratio between the torque applied and the resulting angular acceleration about that axis. It plays the same role in rotational motion as mass does in linear motion. A body's moment of inertia about a particular axis depends both on the mass and its distribution relative to the axis, increasing with mass and distance from the axis.

It is an extensive (additive) property: for a point mass the moment of inertia is simply the mass times the square of the perpendicular distance to the axis of rotation. The moment of inertia of a rigid composite system is the sum of the moments of inertia of its component subsystems (all taken about the same axis). Its simplest definition is the second moment of mass with respect to distance from an axis.

The Niagara Escarpment is an approximately 1,050-kilometre-long (650-mile) discontinuous, arc-shaped but generally northward-facing escarpment, or cuesta, in Canada and the United States. The escarpment begins south of Lake Ontario and circumscribes the top of the Great Lakes Basin running from New York through Ontario, Michigan, and Wisconsin. The escarpment is the cliff over which the Niagara River plunges at Niagara Falls, for which it is named.

The escarpment is a UNESCO World Biosphere Reserve. The reserve has the oldest forest ecosystem and trees in eastern North America.

St. Catharines is the most populous city in Canada's Niagara Region, the eighth largest urban area in the province of Ontario. As of 2021, St. Catharines has an area of 96.20 square kilometres (37.14 sq mi) and 136,803 residents. It lies in Southern Ontario, 51 kilometres (32 mi) south of Toronto across Lake Ontario, and is 19 kilometres (12 mi) inland from the international boundary with the United States along the Niagara River. It is the northern entrance of the Welland Canal. St. Catharines carries the official nickname "The Garden City" due to its 1,000 acres (4 km) of parks, gardens, and trails.

St. Catharines is between the Greater Toronto and Hamilton Area (GTHA) and the Canada–U.S. border at Fort Erie. Manufacturing was the city's dominant industry, as noted by the heraldic motto, "Industry and Liberality". General Motors of Canada, Ltd., the Canadian subsidiary of General Motors, was the city's largest employer, a distinction now held by the District School Board of Niagara. THK Rhythm Automotive, formerly TRW, operates a plant in the city, although in recent years, employment there has shifted from heavy industry and manufacturing to services.

The Ontario Peninsula is the southernmost part of the province of Ontario and of Canada as a whole. It is bounded by Lake Huron on the west, Lake Ontario on the east, and Lake Erie on the south. At its tip, it is separated from Michigan by the Detroit and St. Clair rivers, as well as Lake St. Clair. The peninsula also includes the Bruce and Niagara peninsulas, one projecting into Lake Huron and the other projecting towards New York, from which it is separated by the Niagara River.

The corner of the peninsula that lies on Lake Ontario is known as the Golden Horseshoe and forms Canada's largest population centre. Other large cities include London and Windsor.

Niagara Falls is a group of three waterfalls at the southern end of Niagara Gorge, spanning the border between the province of Ontario in Canada and the state of New York in the United States. The largest of the three is Horseshoe Falls, which straddles the international border of the two countries. It is also known as the Canadian Falls. The smaller American Falls and Bridal Veil Falls lie within the United States.

Formed by the Niagara River, which drains Lake Erie into Lake Ontario, the combined falls have the highest flow rate of any waterfall in North America that has a vertical drop of more than 50 m (164 ft). During peak daytime tourist hours, more than 168,000 m (5.9 million cu ft) of water goes over the crest of the falls every minute.

The Welland Canal is a ship canal in Ontario, Canada, and part of the St. Lawrence Seaway and Great Lakes Waterway. The canal traverses the Niagara Peninsula between Port Weller on Lake Ontario and Port Colborne on Lake Erie, and was built because the Niagara River—the only natural waterway connecting the lakes—was unnavigable due to Niagara Falls. The Welland Canal enables ships to ascend and descend the Niagara Escarpment, and has followed four different routes since it opened.

The Welland Canal passes about 3,000 ships which transport about 40 million tonnes (88 billion pounds) of cargo a year. It was a major factor in the growth of the city of Toronto, Ontario. The original canal and its successors allowed goods from Great Lakes ports such as Cleveland, Detroit, Milwaukee, and Chicago, as well as other heavily industrialized areas of the United States and Ontario, to be shipped to the Port of Montreal or to Quebec City, where they were usually reloaded onto ocean-going vessels for international shipping.