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

full_context: Document 1: Old Indian Agency House: The Old Indian Agency House is located in Portage, Wisconsin. It was added to the National Register of Historic Places in 1972. The house is located near the Portage Canal.
Document 2: Overland Trail: The Overland Trail (also known as the Overland Stage Line) was a stagecoach and wagon trail in the American West during the 19th century. While portions of the route had been used by explorers and trappers since the 1820s, the Overland Trail was most heavily used in the 1860s as an alternative route to the Oregon, California, and Mormon trails through central Wyoming. The Overland Trail was famously used by the Overland Stage Company owned by Ben Holladay to run mail and passengers to Salt Lake City, Utah, via stagecoaches in the early 1860s. Starting from Atchison, Kansas, the trail descended into Colorado before looping back up to southern Wyoming and rejoining the Oregon Trail at Fort Bridger. The stage line operated until 1869 when the completion of the First Transcontinental Railroad eliminated the need for mail service via Thais' stagecoach. Mostly used during the gold rush of 1848.
Document 3: 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.
Document 4: Cross S Ranch Headquarters: The Cross S Ranch Headquarters is a historic building located in farmland 5 mi south of Olustee, Oklahoma. The two-story stone building served as the headquarters of the Cross S Ranch, a cattle ranch founded in 1891. As a major cattle trail passed through the area, the ranch took advantage of the open land to raise free-range cattle. By 1902, the ranch had decreased in size due to homesteaders and raised horses rather than cattle. The ranch eventually became a wheat farm, reflecting a broader shift in Jackson County agricultural production. A larger wheat farm purchased the ranch in the 1970s, and the headquarters building is all that remains of the original property.
Document 5: Chisholm Trail Casino: Chisholm Trail Casino is a casino that opened in Duncan, Oklahoma in October, 2004. The 22,000 sqft casino is owned and operated by the Chickasaw Nation and is open 24 hours daily. Located along the site of the historic Chisholm Trail cattle drive, the casino is five miles north of downtown Duncan on Highway 81, south of Highway 7. Chisholm Trail is owned and operated by the Chickasaw Nation. The casino is 70 miles south of Norman, Oklahoma, and the Nation’s sister gaming facility, Riverwind Casino. Chisholm Trail is 100 miles northwest of WinStar World Casino, another Chickasaw Nation gaming center, located in Thackerville, Oklahoma.
Document 6: Trading Post, Kansas: Trading Post is an unincorporated community in Linn County, Kansas, United States, which is said to be one of the oldest continuously occupied locations in the state. In 1842 a United States Army fort was built there, but it was soon abandoned. The fort remained until probably at least 1900. It was used by troops travelling through the area during the American Civil War and a military post was established in 1861 and lasted until summer 1865. The Battle of Marais des Cygnes was fought here during the American Civil War. The location derives its name from a French trading post established there about 1825.
Document 7: Potter-Blocker Trail: The Potter-Blocker Trail (sometimes called the Potter-Bacon Cutoff), and also just the potter-bacon trail was a trail blazed by Jack Potter used to move cattle to market, starting around 1883. It was a collateral branch of the Great Western Cattle Trail, but was shorter and crossed more unforgiving land. The trail went at least from Hebbronville, Texas up to Albany, TX, intersecting the Western Trail at Alice, Texas.
Document 8: 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.
Document 9: Doaksville, Choctaw Nation: Doaksville is a former settlement, now a ghost town, located in present-day Choctaw County, Oklahoma. It was founded between 1824 and 1831, by people of the Choctaw Indian tribe who were forced to leave their homes in the Southeastern United States and relocate in an area designated in for their resettlement in Indian Territory. The community was named for Joseph Doak, co-owner of the local trading post. The town flourished until the U.S. Army abandoned nearby Fort Towson in 1854, though it remained as the Choctaw capital until 1859, then declined precipitately after being bypassed by a new railroad in 1870. It is now a ghost town and an archaeological preservation site.
Document 10: Oregon Trail: The Oregon Trail is a 2170 mi historic east–west, large-wheeled wagon route and emigrant trail in the United States that connected the Missouri River to valleys in Oregon. The eastern part of the Oregon Trail spanned part of the future state of Kansas, and nearly all of what are now the states of Nebraska and Wyoming. The western half of the trail spanned most of the future states of Idaho and Oregon.
Document 11: 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.
Document 12: Boggy Depot, Oklahoma: Boggy Depot is a ghost town and Oklahoma State Park that was formerly a significant city in the Indian Territory. It grew as a vibrant and thriving town in present-day Atoka County, Oklahoma, United States and became a major trading center on the Texas Road and the Butterfield Overland Mail route between Missouri and San Francisco. After the American Civil War when the MKT Railroad came through, it bypassed Boggy Depot and the town began a steady decline. It was soon replaced by Atoka as the chief city in the area. By the early 20th century, all that remained of the community was a sort of ghost town.
Document 13: Great Western Cattle Trail: The Great Western Cattle Trail was used during the 19th century for movement of cattle and horses to markets in eastern and northern states. The trail was also known as the Western Trail, Fort Griffin Trail, Dodge City Trail, Northern Trail and Texas Trail. It replaced the Chisholm trail when it closed. While it wasn't as well known, it was greater in length, reaching rail-heads up in Kansas and Nebraska and carried longhorns and horses to stock open-range ranches in the Dakotas, Wyoming, Montana, and two provinces in Canada.
Document 14: Southern Emigrant Trail: Southern Emigrant Trail, also known as the Gila Trail, the Kearny Trail, Southern Trail and the Butterfield Stage Trail, was a major land route for immigration into California from the eastern United States that followed the Santa Fe Trail to New Mexico during the California Gold Rush. Unlike the more northern routes, pioneer wagons could travel year round, mountain passes not being blocked by snows, however it had the disadvantage of summer heat and lack of water in the desert regions through which it passed in New Mexico Territory and the Colorado Desert of California. Subsequently, it was a route of travel and commerce between the eastern United States and California. Many herds of cattle and sheep were driven along this route and it was followed by the San Antonio-San Diego Mail Line in 1857-1858 and then the Butterfield Overland Mail from 1858 - 1861.
Document 15: Concho Indian Boarding School: Concho Indian Boarding School (also known as the Cheyenne-Arapaho Boarding School at Concho or Concho Indian School and home to the Concho Demonstration School) was a boarding school for members of the Cheyenne and Arapaho Tribes and later opened to other Native American students. It existed from 1909 to 1983. It was located in central Oklahoma, approximately 1 mile south of Concho, Oklahoma and 4 miles north of El Reno, Oklahoma. The name of the town and school is the Spanish word for "shell" and was named for the Indian agent, Charles E. Shell.
ground_truth: Kansas