Question: What is this Interior Plain called that native Americans such as the Arapaho lived on (other than the Great Plains)?
Context: Plains Indians, Interior Plains Indians or Indigenous people of the Great Plains and Canadian Prairies are the Native American tribes and First Nation band governments who have traditionally lived on the greater Interior Plains (i.e. the Great Plains and the Canadian Prairies) in North America.  Their historic nomadic culture and development of equestrian culture and resistance to domination by the government and military forces of Canada and the United States have made the Plains Indian culture groups an archetype in literature and art for American Indians everywhere. The HIW Wildside Provincial Championship is a professional wrestling heavyweight championship in the professional wrestling promotion, High Impact Wrestling Canada.  The title was established on April 24, 2004 as the HIW Great Plains Provincial Championship.  Michael Allen Richard Clark won the Great Plains Provincial Championship on September 20, 2013 than won the Wildside Provincial Championship on November 20, 2013 in a fatal four way to crown the first champion.  Upon Clark winning the Wildside Provincial Championship, the Great Plains Provincial Championship was unified with it 24 hours later upon regulation changes.  The lineage from the Great Plains Provincial Championship is also recognized. The East European Plain (also called the Russian Plain, predominantly by Russian scientists, or historically the Sarmatic Plain) is a vast interior plain extending east of the North/Central European Plain, and comprising several plateaus stretching roughly from 25 degrees longitude eastward.  It includes the westernmost Volhynian-Podolian Upland, the Central Russian Upland, and on the eastern border, encompasses the Volga Upland.  The plain includes also a series of major river basins such as the Dnepr Basin, the Oka-Don Lowland, and the Volga Basin.  Along the southernmost point of the East European Plain are the Caucasus and Crimean mountain ranges. Together with the North European Plain covering much of north-eastern Poland, the Baltics (Estonia, Latvia and Lithuania), north-eastern Romania, and Moldova it constitutes the European Plain, the mountain-free part of the European landscape. The Arapaho are a tribe of Native Americans from the western Great Plains, in the area of eastern Colorado and Wyoming.  Traditional Arapaho music, described by Bruno Nettl (1965, p. 150), includes sacred and secular songs.  Traditional music uses terraced descent type melodic motion, with songs consisting of two sections, each with a range of more than an octave and scales of four to six tones. Carl Frederick Kraenzel (November 1, 1906 – July 26, 1980) was an American sociologist.  Most of Kraenzel’s work focuses on the people of the Great Plains, covering a range of topics including quality of life, power relations, resource use, and mental health.  Kraenzel has been widely published in a variety of professional journals, monographs, research bulletins, special reports and books in the fields of rural sociology, Great Plains sociology, and natural resource sociology.  His most known work, "The Great Plains in Transition" describes the challenges of social life and connections to the natural environments in the North American semiarid region located between the 98th meridian and the Rocky Mountains.  Born in Hebron, North Dakota, Kraenzel grew up on a farm in the countryside of the Northern Great Plains and witnessed first-hand the challenges of rural life and living in the region.  Kraenzel attended the University of North Dakota for his undergraduate degree, and continued on to do graduate work at the University of Minnesota, Harvard University, and the University of Wisconsin, where he received his Ph.D in 1935.  Kraenzel served as a professor of sociology at Montana State University in Bozeman for many years, and later at the University of Texas at El Paso. Wyoming, a state in the western United States that straddles the intersection of the Rocky Mountains and the Great Plains, had been a part of the traditional geographic expanse of various Native American tribes: the Shoshone, the Arapaho, the Cheyenne, and the Crow.  During the era of Westward Expansion in the late nineteenth and early twentieth centuries, the Crow were pushed north to Montana, where there was already a significant population of their tribe, and the Cheyenne were split between Montana and Oklahoma.  Only the Shoshone and Arapaho remained in Wyoming, with some of both sent to the Wind River Indian Reservation, and others of both pushed to other western states and Oklahoma, respectively.  As such, in total, there are two Native American languages currently spoken in Wyoming: Shoshone and Arapaho. Neotibicen dorsatus, colloquially called the bush cicada or grand western cicada is a species of large bodied annual cicada in the genus "Neotibicen".  Unique among other species of "Neotibicen", this species is almost exclusively associated with Eastern tallgrass prairies and the Great plains region of central North America.  Prior to the European penetration and settlement of the interior of North America, this was among the most widespread and abundant cicada species in the great plains region; inhabiting a sprawling geographic range.  Unfortunately, the extensive destruction of the North American tallgrass prairie for the purposes of agriculture, livestock grazing, and urbanization has precipitated the widespread decline of this species and fragmentation of its distribution.  In certain areas of dense urban development or agricultural activity in its former range, populations have been decimated and the cicada effectively extirpated.  In modern times, it exists in isolated prairie remnants scattered across the great plains.  Although generally listed as a least concern species by conservation groups, remaining relict populations should be monitored and conserved. The Arapaho ( ; in French: "Arapahos, Gens de Vache") are a tribe of Native Americans historically living on the plains of Colorado and Wyoming.  They were close allies of the Cheyenne tribe and loosely aligned with the Lakota and Dakota.  The Arapaho language, "Heenetiit", is an Algonquian language closely related to Gros Ventre (Ahe/A'ananin), whose people are considered to have separated from the Arapaho at an early time.  The Blackfeet and Cheyenne also speak Algonquian languages, but theirs are quite different from Arapaho. The Medicine Lodge Treaty is the overall name for three treaties signed between the Federal government of the United States and southern Plains Indian tribes in October 1867, intended to bring peace to the area by relocating the Native Americans to reservations in Indian Territory and away from European-American settlement.  The treaty was negotiated after investigation by the Indian Peace Commission, which in its final report in 1868 concluded that the wars had been preventable.  They determined that the United States government and its representatives, including the United States Congress, had contributed to the warfare on the Great Plains by failing to fulfill their legal obligations and to treat the Native Americans with honesty. Juan de Ulibarrí or Uribarrí (1670-1716) was a Spanish or Criollo soldier and explorer who lived in New Mexico.  In 1706 he led an expedition to El Cuartelejo on the Great Plains of western Kansas and eastern Colorado.  Ulibarrí's diary survives and is an important source for the history of Spanish exploration of the Great Plains and relationships with the Apache and Pueblo Indians.  The purpose of Ulibarrí's expedition was to find and escort back to New Mexico about 60 people from Picuris Pueblo who had earlier fled Spanish rule in New Mexico and established communities on the Great Plains.  The Cuartelejo Ruins in Kansas are a remnant of the Pueblos who lived on the plains.
Answer: the Canadian Prairies