Question: The Darlington Agency was a stop on the trail that had a northern post in what state?

Context paragraphs:
Darlington Agency: The Darlington Agency was an Indian agency on the Cheyenne and Arapaho Indian Reservation in Canadian County, Oklahoma.  The agency was established in 1870, when the agency established at Fort Supply the previous year was moved to a more accessible location for the tribes.  Brindon Darlington, a Quaker for whom the agency was named, was the first agent at the agency, a position he held until his death in 1872.  The agency gained a post office and an Indian school run by John Homer Seger, and it became a stop on the Chisholm Trail.  By 1880, the agency had its own newspaper, the "Cheyenne Transporter"; it was the first in western Oklahoma.  The Cheyenne left to form their own agency at Concho in 1897; when the Arapaho reunited with them, they both occupied the Concho agency, and the Darlington Agency became the property of the State of Oklahoma.  The Masons used the site for a boarding school and retirement home until 1922; the state then briefly used the site as a drug rehabilitation center before making it the Oklahoma Department of Wildlife Conservation's main bird hatchery and research station.

Seger Indian Training School: The Seger Indian Training School was a historic school on the eastern edge of Colony, Oklahoma.  John Homer Seger, a white settler in the Indian Territory, founded the school in 1893.  Seger had come to the Darlington Agency in 1875 to work as a teacher, and he established the Seger Colony (the predecessor of Colony) in 1886 with 120 Arapaho.  His school taught farming and industrial skills to Native Americans until it closed in 1941; one of the buildings later became Colony's public school.

West Grouse Creek Trail: West Grouse Creek Trail is in the northern Sawatch Range, part of the Rocky Mountains in the U.S. state of Colorado.  It is located in the Holy Cross Wilderness east of Grouse Mountain and south of Beaver Creek Resort in Eagle County.  West Grouse Creek Trail is south of Interstate 70, near Minturn, west of Vail and east of Avon, Colorado.  West Grouse Creek Trailhead, elevation 7,880 feet, is about a half-mile north of Minturn, six miles west of Vail.  West Grouse Creek Trail ascends four miles before meeting a junction with the short Olsen Lake Trail, at 11,200 feet.  The trail continues winding southwest through a dense forest of spruce and fir trees to a tundra basin below the summit of Grouse Mountain.  The Grouse Mountain Trail merges with the West Grouse Creek Trail, at 11,500 feet elevation, in the tundra meadow.  Grouse Mountain Trail continues southwest to Grouse Mountain Pass, six miles from the trailhead, at 12,000 feet.  Following the Grouse Mountain Trail southeast leads to the Martin Creek Trail and Cross Creek Trail, north of Mount of the Holy Cross.  Hiking Colorado: Holy Cross Wilderness, a hiking guide by Kim Fenske, provides a description of West Grouse Creek Trail.

Owl Creek Trail: The Owl Creek Trail is a 7.3 mi long hiking trail in the far northern region of Grand Teton National Park in the U.S. state of Wyoming.  The trail begins at a junction on the Berry Creek Trail and traverses west then south to Moose Basin Divide where it meets the Webb Canyon Trail.  Located in the remote northern backcountry of Grand Teton National Park, the trail is not connected to maintained trails in the southern part of the park and must be accessed from the Glade Creek trailhead in the John D. Rockefeller, Jr.  Memorial Parkway.  From Glade Creek, it is a 7.5 mi hike to the Berry Creek Trail and then another 4 mi to the trail junction.  The Owl Creek Trail follows Owl Creek west then south and passes south of Forellen Peak.  The trail requires numerous stream crossings which can be dangerous during spring melt.

The Northern Post: The Northern Post was a newspaper that operated from Aliwal North in the Cape Colony, from 1874 to 1902.

Fort Robinson massacre: The Fort Robinson tragedy (winter 1878-1879) refers to a series of events which occurred during the winter of 1878-1879 at Fort Robinson in northwestern Nebraska.  After having been forced to relocate south to the Darlington Agency in the Southern Cheyenne Reservation, a band of Northern Cheyenne fled back north in September 1878 because of the terrible conditions.  The US Army intercepted part of the Northern Cheyenne Exodus and took a band of nearly 150 Cheyenne to Fort Robinson in Nebraska.

John Homer Seger: John Homer Seger (February 23, 1846 – February 6, 1928) was an American educator best known for his work with the Arapaho tribe in Oklahoma.  Seger was born in Geauga County, Ohio, and grew up in Illinois.  He joined the Union Army in 1864; after the war, he worked in Wisconsin and Kansas.  In 1872, Seger took a position as a mason and carpenter for a new school at the Darlington Agency on the Cheyenne-Arapaho Indian Reservation in what was then the Indian Territory.  When the school opened in 1875, Seger became its first superintendent, a position he held until 1882.

Chisholm Trail: The Chisholm Trail was a trail used in the post-Civil War era to drive cattle overland, from ranches in Texas to Kansas railheads.  The portion of the trail marked by Jesse Chisholm went from his southern trading post near the Red River, to his northern trading post near Kansas City, Kansas.

New England National Scenic Trail: The New England National Scenic Trail (NET) is a National Scenic Trail in southern New England, which includes most of the three single trails Metacomet-Monadnock Trail, Mattabesett Trail and Metacomet Trail.  After the Metacomet-Monadnock-Mattabesett trail system, the trail is sometimes called the Triple-M Trail.  The 215 mi route extends through 41 communities from Guilford, Connecticut at Long Island Sound over the Metacomet Ridge, through the highlands of the Pioneer Valley of Massachusetts, to the New Hampshire state border.  (The remainder of the M-M Trail to the summit of Mount Monadnock in southern New Hampshire is not included in the designation.)  This includes a now (2013) complete connector trail (the Menunkatuck Trail) from the southernmost location of the Mattabesett Trail (in northern Guilford, Connecticut) to the sea (Long Island Sound) and a deviation of the Metacomet-Monadnock Trail in Massachusetts, to lead the trail through state-owned land instead of largely unprotected land.

Hart-Montague Trail State Park: William Field Memorial Hart-Montague Trail State Park, previously and more commonly known as Hart-Montague Trail State Park, is a linear state park in Michigan that consists of a bicycle trail running from the city of Montague in Muskegon County to the city of Hart in Oceana County.  Recognizing its potential, Bill Field of Shelby purchased the former railroad and donated it for trail use to the State of Michigan.  Opened in 1991 and officially adopted as a Rails to Trails park in 1996, it was one of the first "Rails to Trails" projects in the State of Michigan.  Its success paved the way for more trails throughout the state and Midwest.  The trail's total length was previously 22 mi ; however continuous expansions have increased that length in recent years with the hope of linking it to other trails throughout Western Michigan.  A number of local businesses, such as restaurants and ice cream parlors, in the towns along the trail have posted small, discreet signage near the trail to attract cycling visitors who might not otherwise ever notice the little shops in the intervening small municipalities.  A whimsically themed ice cream/dairy bar in New Era, roughly halfway along the trail, is often mentioned by trail visitors, although there are also a number of others spread along the trail.  There is a bicycle rental shop on Thompson St in Montague in the south, a repair shop right off the trail in Mears as well as another rental shop on Silver Lake Rd in Mears several miles away from the northern section of the trail.

Supporting paragraphs: Darlington Agency Chisholm Trail
Answer: Kansas