Question: Last of the Wild Horses was filmed in Medford, Oregon, which is the county seat of what county?

Context paragraphs:
Medford, Oregon: Medford is a city in, and county seat of, Jackson County, Oregon, United States.  As of July 1, 2014, the city had a total population of 78,557 and a metropolitan area population of 208,545, making the Medford MSA the fourth largest metro area in Oregon.  The city was named in 1883 by David Loring, civil engineer and right-of-way agent for the Oregon and California Railroad, suggested by Medford, Massachusetts, near his home town of Concord, Massachusetts, and in recognition of its supposed position near the middle ford of Bear Creek.

Jackson County Courthouse (Medford, Oregon): Jackson County Courthouse is an Art Deco building in Medford, Oregon, United States that was built in 1932, six years after county residents voted to move the county seat from Jacksonville to Medford.

James Wild Horse Trap: The James Wild Horse Trap in Nye County, Nevada, near Fish Springs, is a historic site that is listed on the U.S. National Register of Historic Places.  It was the location of a corral and fences used to capture wild horses, built out of dead Juniper trees.  It is as described in a book by Will James, "Sand", or "Lone Cowboy", published by Charles Scribners Son's in 1930.

Carova Beach, North Carolina: Carova Beach or Carova is an unincorporated community in Currituck County in the extreme northeast corner of North Carolina, United States.  The community, begun in the 1960s, is found on Currituck Banks, north of Bodie Island, and can only be accessed by boat or by four-wheel drive vehicle.  There are no paved roads connecting Carova to the town of Corolla, North Carolina.  The neighboring settlement of Sandbridge in Virginia Beach, Virginia is not accessible by vehicle from Carova.  In the 1960s when development began in Carova there were plans to construct a paved road from the Sandbridge south to Carova through the Back Bay National Wildlife Refuge but these never materialized.  Today there is a permanent fence from ocean to sound to keep vehicles from crossing but, more importantly, to keep the wild horses from migrating to the Virginia side of the border.  To reach Carova, four-wheel drive vehicles must drive north along the beach from Corolla into the community, as access from Virginia is limited to pedestrians and bicyclists.

Last of the Wild Horses: Last of the Wild Horses is a 1948 American Western film starring Jane Frazee.  It was featured in episode 611 of "Mystery Science Theatre 3000".  Filming took place in Jacksonville, Oregon, USA, Medford, Oregon, USA and Rogue River Valley, Oregon, USA.

Jackson County, Oregon: Jackson County is a county in the U.S. state of Oregon.  As of the 2010 census, the population was 203,206.  The county seat is Medford.  The county is named for Andrew Jackson, the seventh president of the United States.

Sheldon National Wildlife Refuge: The Sheldon National Wildlife Refuge is a 573,504 acre national wildlife refuge on the northern border of the U.S. state of Nevada.  A very small part extends northward into Oregon.  It is managed by the United States Fish and Wildlife Service (USFWS) as the Nevada component of the Sheldon-Hart Mountain National Wildlife Refuge Complex, which is headquartered in Lakeview, Oregon.  The Sheldon Refuge is noted for its population of wild horses.

Wild Horse Mesa (1925 film): Wild Horse Mesa is a 1925 American Western silent film directed by George B. Seitz and starring Jack Holt, Noah Beery, Sr., Billie Dove, and Douglas Fairbanks, Jr. Based on the novel "Wild Horse Mesa" by Zane Grey, the film is about a rancher who, desperate for money, decides to trap and sell wild horses using barbed wire.  The local Navajo tribe tries to persuade him not to do it.  The film was produced by Famous Players-Lasky and released by Paramount Pictures.  "Wild Horse Mesa" was filmed on location in Colorado.  Prints of the film have survived.

Medford, Wisconsin: Medford is a city in Taylor County, in north-central Wisconsin, United States.  The population was 4,326 at the 2010 census.  The city is located mostly within the boundaries of the Town of Medford.  It is the county seat of Taylor County.

Grants Pass, Oregon: Grants Pass is a city in, and the county seat of, Josephine County, Oregon, United States.  The city is located on Interstate 5, northwest of Medford.  Attractions include the Rogue River, famous for its rafting, and the nearby Oregon Caves National Monument located 30 miles (48 km) south of the city.  Grants Pass is 256 miles (412 km) south of Portland, the largest city in Oregon.  The population was 34,533 at the 2010 census.

Supporting paragraphs: Last of the Wild Horses Medford, Oregon
Answer: Jackson County