Question: How long is the main river that is located in Oxford County, Maine?

Context articles: Oxford Hills Comprehensive High School
Bear River (Long Lake)
Humptulips River
Kittanning, Pennsylvania
Marked Tree Lock and Siphons
Brownfield, Maine
Oxford County Regional Airport
Tenmile River (Maine)
Oxford, Maine
Oxford County, Ontario

Oxford Hills Comprehensive High School is a public high school in South Paris, Oxford County, Maine.
 Part of Maine School Administrative District 17, the school serves Oxford, South Paris, Norway, West Paris, Waterford, Hebron, Harrison and Otisfield.
The Bear River is a 2.7 mi tributary of Long Lake in the U.S. state of Maine.
 It originates at the outlet of Bear Pond in the town of Waterford in Oxford County, then flows southeast into the town of Bridgton in Cumberland County and finally the town of Harrison, where it reaches Long Lake.
 Via Long Lake, the Songo River, and Sebago Lake, the Bear River is part of the Presumpscot River watershed, flowing to Casco Bay on the Atlantic Ocean.
The Humptulips River is a river in Grays Harbor County, Washington, in the United States.
 Its main tributaries are the East Fork Humptulips River, about 20 mi long (32 km), and West Fork Humptulips River, about 30 mi long (48 km).
 After the forks join, the main river is approximately 20 miles (32 km) long.
Kittanning ( pronounced ) is a borough and the county seat of Armstrong County in the U.S. state of Pennsylvania.
 It is situated 44 mi northeast of Pittsburgh, along the east bank of the Allegheny River.
 The name "Kithanink" means 'on the main river' in the Delaware language, from "kit-" 'big' + "hane" 'mountain river' + -"ink" (suffix used in place names).
 "The main river" is a Lenape epithet for the Allegheny and Ohio, considered as all one river.
 The borough and its bridge were used as a setting for several recent films.
The Marked Tree Lock and Siphons are a flood control facility on the St. Francis River in Poinsett County, Arkansas.
 These facilities are located about 9 mi north of Marked Tree.
 Built in 1926, the lock is located on a now disused and partially filled artificial channel west of the main river.
 It has a concrete trough about 130 ft long and 30 ft high, with a small brick control house from which four gates are operated to regulate water flow through the lock.
 The lock gates have been removed and that area filled in and topped by a roadway.
 The siphons are located on a levee that impounds the main river channel several hundred feet upstream from the lock, and consist of a series large metal tubes, whose ends are mounted in submerged concrete structures above and below the levee.
 The siphons were built in 1939 to solve the problem of water flow regulation in the wake of repeated major flooding events on the river, and are described by the United States Army Corps of Engineers as unique in the nation for their scope and efficiency.
Brownfield is a town in Oxford County, Maine, United States.
 The population was 1,597 at the 2010 census.
 Brownfield is home to the Stone Mountain Arts Center.
Oxford County Regional Airport (FAA LID: 81B) is a county owned, public use airport in Oxford County, Maine, United States.
 It is located two nautical miles (4 km) east of the central business district of Oxford, Maine.
 This airport is included in the National Plan of Integrated Airport Systems for 2011–2015, which categorized it as a "general aviation" facility.
The Tenmile River is an 8.6 mi river in the towns of Hiram and Brownfield in western Maine in the United States.
 It is a tributary of the Saco River, which flows to the Atlantic Ocean.
Oxford is a town in Oxford County, Maine, United States.
 The population was 4,110 at the 2010 census.
 Oxford is home to the Oxford Plains Speedway, the annual Oxford County Fair, and Oxford Casino.
 The town includes the village of Welchville.
Oxford County is a regional municipality of the Canadian province of Ontario, located in the Southwestern portion of the province.
 The regional seat is in Woodstock.
 Oxford County has functioned as a regional municipality since 2001, despite still containing the word "county" in its official title.
 It comprises a single Statistics Canada census division.