Title: History of wolves in Yellowstone
Content:  Prior to the National Park Service assuming control of the park in 1916, the U.S. Army killed 14 wolves during their tenure (1886&ndash;1916), most in the years 1914&ndash;15. In 1940, Adolph Murie, a noted wildlife biologist published his Fauna Series No. 4&mdash;Fauna of the National Parks of the United States-Ecology of the Coyote in the Yellowstone National Park. In this report, Murie tallied the number of wolves killed as reported annually by park administrators between 1915 and 1935: Updated research in the 1980s verified that the last official killing of wolves in the park took place in 1926 when two pups found near Soda Butte Creek were killed by park rangers. The last reported wolf killed in the Greater Yellowstone Ecosystem (prior to today's legal hunting or control measures) occurred in May 1943 when Leo Cottenoir, a Native American sheepheader on the Wind River Reservation shot a wolf near the southern border of the park.
Title: List of animals of Yellowstone
Content:  Northern Rocky Mountain wolves, a subspecies of the gray wolf (Canis lupus), were native to Yellowstone when the park was established in 1872. Predator control was practiced in the late 19th and early 20th centuries. Between 1914 and 1926, at least 136 wolves were killed in the park; by the 1940s, wolf packs were rarely reported. By the 1970s, scientists found no evidence of a wolf population in Yellowstone; wolves persisted in the lower 48 states only in northern Minnesota and on Isle Royale in Michigan. Canadian grey wolves were introduced into Yellowstone in 1995. This move has returned wolves to land that was once ruled by the canine. They currently exist in several packs, the largest of which are the Slough 
Title: Yellowstone National Park
Content:  on public lands. Park Service hunters carried out these orders, and by 1926 they had killed 136 wolves. Gradually, wolves were virtually eliminated from Yellowstone. Further exterminations continued until the National Park Service ended the practice in 1935. With the passing of the Endangered Species Act in 1973, the wolf was one of the first mammal species listed. After the wolves were extirpated from Yellowstone, the coyote then became the park's top canine predator. Since the coyote is not able to bring down large animals, this lack of an apex predator resulted in a marked increase in lame and sick megafauna. 
Title: History of wolves in Yellowstone
Content:  included words that authorized the Secretary of the Interior to "provide in his discretion for the destruction of such animals and of such plant life as may be detrimental to the use of said parks, monuments and reservations". It is generally accepted that sustainable gray wolf packs had been extirpated from Yellowstone National Park by 1926, although the National Park Service maintained its policies of predator control in the park until 1933. However, a 1975&ndash;77 National Park Service sponsored study revealed that during the period 1927 to 1977, there were several hundred probable sightings of wolves in the park. Between 1977 and the re-introduction in 1995, there were additional reliable sightings of wolves in the park, most believed to be singles or pairs transiting the region.
Title: Northern Rocky Mountain wolf
Content:  Early recorded history of the northern Rocky Mountain wolf found it roaming primarily in the forests that would later become known as Yellowstone National Park. They resided nearby Native Americans of the Tukudika tribe, who considered the wolf to be a sacred animal. As the American population began spreading west in the late 19th century, ranchers, farmers, and cattle drivers began to settle in the area. In due time, the northern Rocky Mountain wolf began preying on the livestock brought by the settlers. A practice of eradication was enacted in 1915, through the use of guns, traps, and poison. This policy was made even more all encompassing by the creation of the National Park Service in 1916, which regulated control over the land in Yellowstone and authorized through the National Park Service Organic Act the "destruction of such animals and such plant life that may be detrimental". By 1924, the last known wolves in the bounds of Yellowstone were killed, though small numbers of the northern Rocky Mountain wolf survived in outlying areas.
Title: Ecology of the Rocky Mountains
Content: Greater Yellowstone Area: 460 ; Central Idaho: 684 Wolves once were common throughout the Rocky Mountains. They were shot, poisoned, and trapped into local extinction by early settlers and federal agents. The last Gray wolf in Colorado was killed in 1940, and the wolf was first listed as an endangered species in 1967. Wolves from southeastern British Columbia recolonized northwestern Montana in 1986; by 1994 the population had grown to 7 packs and about 70-75 wolves. Wolves from Glacier National Park have dispersed naturally as far away as northeastern Idaho and just south of Yellowstone National Park. A wolf was shot near Yellowstone National Park in 1992. From January to March 1995, 15 adult wolves 
Title: History of wolves in Yellowstone
Content:  The History of wolves in Yellowstone included extirpation, absence and reintroduction of the gray wolf (Canis lupus) to Yellowstone National Park. The reintroduction of wolves was controversial as it is with the worldwide reintroduction of wolves. When Yellowstone National Park was created in 1872, wolf populations were already in decline in Montana, Wyoming and Idaho. The creation of the national park did not provide protection for wolves or other predators, and government predator control programs in the first decades of the 1900s essentially helped eliminate the gray wolf from Yellowstone. The last wolves were killed in Yellowstone in 1926. After that, sporadic reports of wolves still occurred, but scientists confirmed that sustainable wolf populations had been extirpated and were absent from Yellowstone during the mid-1900s. Starting in the 1940s, park managers, biologists, conservationists and environmentalists began what would ultimately turn into a campaign to reintroduce the gray wolf into Yellowstone National Park. When the Endangered Species Act of 1973 was passed, the road to legal reintroduction was clear. In 1995, gray wolves were reintroduced into Yellowstone in the Lamar Valley.
Title: Yellowstone National Park
Content:  during that interval. Almost all the wolves documented were descended from the 66 wolves reintroduced in 1995–96. The recovery of populations throughout the states of Wyoming, Montana and Idaho has been so successful that on February 27, 2008, the U.S. Fish and Wildlife Service removed the Northern Rocky Mountain wolf population from the endangered species list. Black bears are common in the park and were a park symbol due to visitor interaction with the bears starting in 1910. Feeding and close contact with bears has not been permitted since the 1960s to reduce their desire for human foods. Yellowstone is one 
Title: Soda Butte Creek
Content:  A wolf pack re-introduced in 1995 was called the Soda Butte Pack. It was later renamed the Yellowstone Delta Pack in 2000 after all the originals members of the pack died.
Title: History of wolves in Yellowstone
Content:   In January 1995, U.S. and Canadian wildlife officials captured 14 wolves from multiple packs east of Jasper National Park, near Hinton, Alberta, Canada. These wolves arrived in Yellowstone in two shipments—January 12, 1995 (8 wolves) and January 20, 1995 (6 wolves). They were released into three acclimation pens—Crystal Creek, Rose Creek and Soda Butte Creek in the Lamar Valley in Northeast East Yellowstone National Park. In March 1995, the pens were opened and between March 21 and March 31, 1995, all 14 wolves were loose in Yellowstone. Seventeen additional wolves captured in Canada arrived in Yellowstone in January 1996 and were released into the park in April 1996 from the Chief Joseph, Lone Star, Druid Peak and Nez Perce pens. These were the last wolves released into the park as officials believed that the natural reproduction and survival were sufficient to obviate additional releases.

Question: when was the last wolf pack killed in yellowstone?
Answer: 1926.
by 1926.