Question: What city is the seat of the county that includes the town of Jaffrey, New Hampshire?

Context articles: Jaffrey Mills
Contoocook Lake
Amos Learned Farm
Jaffrey (CDP), New Hampshire
Jaffrey Center Historic District
East Jaffrey Historic District
Jaffrey Airport–Silver Ranch
Cheshire County, New Hampshire
Fort Stark
Amos Fortune

The Jaffrey Mills is a historic mill complex at 41 Main Street, in the central business district of Jaffrey, New Hampshire.
 It consists of a connected series of primarily brick buildings flanking the Contoocook River just north of Main Street.
 Its oldest buildings, the original mill and office building, are on the west side of the river.
 They were built in 1868, and feature mansard roofs and banded dentil brick cornices.
 The mill building has a tower that originally sported a cupola, but this was removed early in the 20th century.
 In 1872 the building on the east side was built, and the two sides joined by timber-frame bridges were added in 1897, at the same time the east building was extended northward.
 Later additions to the north of the east building include a storage area and a loading dock.
Contoocook Lake ( ) is a 344 acre water body located in Cheshire County in southwestern New Hampshire, United States, in the towns of Jaffrey and Rindge.
 The lake, along with Pool Pond, forms the headwaters of the Contoocook River, which flows north to the Merrimack River in Penacook, New Hampshire.
The Amos Learned Farm is a historic farmstead on New Hampshire Route 137 (Lower Jaffrey Road) in Dublin, New Hampshire.
 This 1-1/2 story wood frame Cape style house was built c. 1808 by Benjamin Learned, Jr., son of one of Dublin's early settlers; he deeded the property to his brother Amos that year.
 Both of the Learneds eventually moved to Maine.
 The house stands near a discontinued road that went to the Upper Jaffrey Road, where their father's house stands.
Jaffrey is a census-designated place (CDP) and the main village in the town of Jaffrey in Cheshire County, New Hampshire, United States.
 The population of the CDP was 2,757 at the 2010 census, out of 5,457 people in the entire town of Jaffrey.
The Jaffrey Center Historic District encompasses the traditional civic heart of the small town of Jaffrey, New Hampshire.
 The district lies to the west of the Jaffrey's main business district, extending along Main Street (New Hampshire Route 124) from Harkness Road to the Jaffrey Common, and along Thorndike Pond Road northward from Main Street.
 The district retains the feel of an 18th-19th century rural village, and includes elements dating to shortly after the town's incorporation in 1773.
 The old burying ground was established in 1774, and the old meeting house (now a cultural center) was raised in 1775.
 The district includes 19th century school houses, and houses that were built in the 18th and 19th centuries, in predominantly Georgian, Federal, and Greek Revival styles.
 One of the town's early industries is also represented, in the remnants of a tannery established c. 1810 at the east end of the district.
The East Jaffrey Historic District is a historic district running roughly along NH Route 124 (Main Street) through Jaffrey, New Hampshire.
 It encompasses what is now the economic and civic heart of the town, centered on the Jaffrey Mills and the crossing of the Contoocook River by Route 124.
 It extends as far west as St. Patrick's Church beyond Charlonne Street and as far east as the US Post Office building at Route 124 and Ellison Street.
 To the north it extends along Peterborough Street (United States Route 202) to Christian Court, and to the south it extends along River Street (also US 202) and School Street to their junction.
 The district includes early 19th-century residential structures, as well as industrial buildings and housing associated with the Jaffrey Mills which arose in the mid-19th century.
 The area was known as "East Jaffrey" prior to its rise in economic ascendancy over what is now Jaffrey Center, the center of Jaffrey when it was chartered in 1773.
Jaffrey Airport–Silver Ranch is a public use airport in Cheshire County, New Hampshire, United States.
 It is owned by the Jaffrey Municipal Airport Development Corp. and is located one nautical mile (1.85 km) southeast of the central business district of Jaffrey, New Hampshire.
 It is included in the Federal Aviation Administration (FAA) National Plan of Integrated Airport Systems for 2017–2021, in which it is categorized as a general aviation facility.
Cheshire County is a county located in the southwestern portion of the U.S. state of New Hampshire.
 As of the 2010 census, the population was 77,117.
 Its county seat is the city of Keene.
 Cheshire was one of the five original counties of New Hampshire, and is named for the county of Cheshire in England.
 It was organized in 1771 at Keene.
Fort Stark is a former military fortification in New Castle, New Hampshire, United States.
 Located at Jerry's Point (also called Jaffrey's Point) on the southeastern tip of New Castle Island, most of the surviving fort was developed in the early 20th century, following the Spanish–American War, although there were several earlier fortifications on the site, portions of which survive.
 The fort was named for John Stark, a New Hampshire officer who distinguished himself at the Battle of Bennington in the American Revolution.
 The purpose of Fort Stark was to defend the harbor of nearby Portsmouth and the Portsmouth Naval Shipyard.
 The fort remained in active use through the Second World War, after which it was used for reserve training by the US Navy.
 The property was partially turned over to the state of New Hampshire in 1979, which established Fort Stark Historic Site, and the remainder of the property was turned over in 1983.
 The grounds are open to the public during daylight hours.
Amos Fortune (c. 1710 – November 1801) was a prominent African-American citizen of Jaffrey, New Hampshire in the 18th century.
 Fortune was born in Africa and brought to America as a slave.
 He purchased his freedom at the age of 60 and moved to Jaffrey to start a leather tannery business.
 Documents now archived at the Jaffrey Public Library testify to his literacy, community position, and financial success.