Question: Charles Albert Varnum received a Medal of Honor for his role in a conflict at Drexel Mission following a massacre that occured on what Indian reservation?

Context paragraphs:
Plenty Horses: Plenty Horses ("Tasunka") (b. 1869) was a Sicangu (Brulé) Lakota from the Rosebud Indian Reservation.  On January 7, 1891, eight days after the Wounded Knee Massacre, he shot and killed Army Lieutenant Edward W. Casey, commandant of the Cheyenne Scouts (designated Troop L, Eighth Cavalry) two miles north of the Stronghold Table in the Badlands of the Pine Ridge Indian Reservation in South Dakota.  Plenty Horses – who was present at the Drexel Mission Fight the day after the Wounded Knee Massacre, was arrested for the murder and his case went to trial.  His defense was he shot and killed Casey as an effort to redeem himself in the eyes of his people after having spent five years at the Carlisle Indian School learning the ways of the white man.  He returned in time to be present on the reservation during the massacre.

Charles Varnum: Charles Albert Varnum (June 21, 1849 – February 26, 1936) was a career United States Army officer.  He was most noted as the commander of the scouts for George Armstrong Custer in the Little Bighorn Campaign (of which he was the last of the surviving officers to die of natural causes) during the Great Sioux War, as well as receiving the Medal of Honor for his actions in a conflict at Drexel Mission following the Wounded Knee Massacre.

Wind River Indian Reservation: Wind River Indian Reservation is an Indian reservation made for the Eastern Shoshone and Northern Arapaho Native American tribes in the central western portion of the U.S. state of Wyoming.  It is the seventh-largest Indian reservation by area in the United States, encompassing a land area of 3,473.272 sq mi (8,995.733 km²), or land and water area of 3,532.010 sq mi (9,147.864 km²).  The reservation constitutes just over one-third of Fremont County and over one-fifth of Hot Springs County.

United States v. Quiver: United States v. Quiver, 241 U.S. 602 (1916) is a case decided by the United States Supreme Court after first appearing in United States District Court for the District of South Dakota.  The case argued on February 28, 1916 and decided on June 12, 1916 concerned adultery committed on the Pine Ridge Indian Reservation in South Dakota between two enrolled members of the Oglala Sioux Tribe.  The district court had held that adultery committed by an Indian with another Indian on an Indian reservation was not punishable under the act of March 3, 1887, c. 397, 24 Stat.  635, now § 316 of the Penal Code.  This decision was made because the offense occurred on a Sioux Indian reservation which is not said to be under jurisdiction of the district court.  The United States Supreme Court affirmed the judgment of the district court saying that the adultery was not punishable as it had occurred between two American Indians on an American Indian reservation.

Malheur Indian Reservation: The Malheur Indian Reservation was an Indian reservation established for the Northern Paiute in eastern Oregon and northern Nevada from 1872 to 1879.  The federal government "discontinued" the reservation after the Bannock War of 1878, under pressure from European-American settlers who wanted the land, a negative recommendation against continuing it by its agent William V. Rinehart, the internment of more than 500 Paiute on the Yakama Indian Reservation, and reluctance of the Bannock and Paiute to return to the lands after the war.

Umatilla Indian Reservation: The Umatilla Indian Reservation is an Indian reservation in the Pacific Northwest of the United States.  It lies in northeastern Oregon, east of Pendleton.  The reservation is mostly in Umatilla County, with a very small part extending south into Union County.  It is managed by the three Confederated Tribes of the Umatilla Indian Reservation.

Mille Lacs Indian Reservation: Mille Lacs Indian Reservation is the popular name for the land-base for the Mille Lacs Band of Ojibwe in Central Minnesota, about 100 miles (160 km) north of Minneapolis-St.  Paul.  The contemporary Mille Lacs Band reservation has significant land holdings in Mille Lacs, Pine, Aitkin and Crow Wing counties, as well as other land holdings in Kanabec, Morrison, and Otter Tail Counties.  Mille Lacs Indian Reservation is also the name of a formal Indian reservation established in 1855.  It is one of the two formal reservations on which the contemporary Mille Lacs Band retains land holdings.  The contemporary Mille Lacs band includes several aboriginal Ojibwe bands and villages, whose members reside in communities throughout central Minnesota.

Drexel Mission Fight: The Drexel Mission Fight was an armed confrontation between Lakota warriors and the United States Army that took place on the Pine Ridge Indian Reservation in South Dakota on December 30, 1890, the day after the Wounded Knee Massacre.  The fight occurred on White Clay Creek approximately 15 miles north of Pine Ridge where Lakota were purported to have burned the Catholic Mission.

St. Elizabeth's Convent: St. Elizabeth's Convent is a historic Roman Catholic convent located at 1663 Bristol Pike in Cornwells Heights, Bensalem Township, Bucks County, Pennsylvania.  It's formerly known as the Sisters of the Blessed Sacrament for Indians and Colored People and now the home to Saint Katharine Drexel Mission Center and National Shrine.  The complex was built in 1892, and consists of three contributing buildings.  They are built in the Spanish-French Mission style .  The main building is the convent which has an attached chapel and bell tower.  The other contributing buildings are the utility building and 2 ⁄ -story laundry building.  It served as the national headquarters and motherhouse for the Sisters of the Blessed Sacrament for Indians and Colored People, founded by Saint Katharine Drexel.  Saint Katharine is entombed in a crypt in the chapel.

Wounded Knee Massacre: The Wounded Knee Massacre (also called the Battle of Wounded Knee) occurred on December 29, 1890, near Wounded Knee Creek (Lakota: "Čhaŋkpé Ópi Wakpála") on the Lakota Pine Ridge Indian Reservation in the U.S. state of South Dakota.

Supporting paragraphs: Charles Varnum Wounded Knee Massacre
Answer: Lakota Pine Ridge Indian Reservation