Question: When were bison introduced at Golden Gate Park?
About the article "Golden Gate Park", section "Bison paddock".

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Bison ("Bison bison") have been kept in Golden Gate Park since 1891, when a small herd was purchased by the park commission.
At the time, the animal's population in North America had dwindled to an all-time low, and San Francisco made a successful effort to breed them in captivity.
In 1899, the paddock in the western section of the park was created.
At its peak and through a successful captive breeding program, more than 100 calves were produced at Golden Gate Park, helping preserve the iconic bison population numbers in North America, which has been critical to the culture and livelihood of Native Americans.
In 1984, Mayor Dianne Feinstein's husband, Richard C. Blum, purchased a new herd as a birthday present for his wife.
The older bison in the paddock today are descendants of those animals.
In December 2011, after the number of bison in the paddock had dwindled to three, Assemblywoman Fiona Ma’s office led another preservation effort.
With donations from the Theodore Rosen Charitable Foundation, Richard C. Blum, and the Garen Wimer Ranch, Assemblywoman Ma’s office worked with the San Francisco Zoo and SF Recreation and Parks to add seven new bison to the existing herd.
The Paddock is currently open to the public for viewing.
Antelope Island in Great Salt Lake, Utah, is part of Antelope Island State Park.
On the island, a semi–free-ranging population of American bison ("Bison bison, "buffalo) has been in existence since 1893.
Though the island was named for the pronghorn antelope that John C. Frémont and Kit Carson found there when they explored the Great Salt Lake, bison were later introduced and the island is now perhaps most famous for its bison herd.
The Antelope Island bison herd is significant because it is one of the largest and oldest publicly owned bison herds in the nation.
It is one of the two bison herds managed by the State of Utah, the other being the Henry Mountains bison herd.
The Antelope Island bison herd currently numbers between 550 and 700 individuals.
Other large free-ranging, publicly controlled herds of bison in the United States include the Yellowstone Park bison herd (3,500 bison), the herd in Custer State Park, South Dakota (1,300 bison), the Henry Mountains bison herd in south-central Utah (300 to 500 animals), the herd at Wind Cave National Park in South Dakota (350 bison), and the 400-strong National Bison Range Herd near Flathead Lake, Montana.
In addition, though the bison on Antelope Island are Prairie bison, which was the most common bison subspecies in North America, the bison have a distinct genetic heritage from many of the other bison herds in the United States and they are considered to be desirable as part of the breeding and foundation stock for other bison herds, because of their separate genetic heritage and some of the distinct genetic markers that are found in the population.
Buffalo watching is one of the most popular activities on Antelope Island.
In fact, the island is perhaps best known for the bison that inhabit it, and the bison are generally easily found and observed. 
The Yellowstone Park bison herd in Yellowstone National Park is probably the oldest and largest public bison herd in the United States.
Yellowstone is known for its geothermal activity and large mammals, especially elk, wolves, American bison, bears, pronghorns, moose and bighorn sheep.
The Yellowstone Park bison herd was estimated in 2011 at approximately 3,700 individuals in two major sub-herds.
The bison in the Yellowstone Park bison herd are American bison of the Plains bison subspecies.
Yellowstone National Park may be the only location in the United States where free-ranging bison were never extirpated, since they continued to exist in the wild and were not re-introduced, as has been done in most other bison herd areas.
Other large free-ranging, publicly controlled herds of bison in the United States include the Wind Cave bison herd (approximately 350 animals), the Antelope Island bison herd (approximately 550 to 700 animals), the Henry Mountains bison herd in Utah (400 to 500 animals), and the National Bison Range herd near Flathead Lake, Montana (400 animals). 
Large Mammals.
American Bison.
Bison are the largest grazing mammals in Yellowstone National Park.
They are strictly vegetarian, a grazer of grasslands and sedges in the meadows, the foothills, and even the high-elevation, forested plateaus of Yellowstone.
Bison males, called bulls, can weigh upwards of 1,800 pounds.
Females (cows) average about 1,300 pounds.
Both stand approximately six feet tall at the shoulder, and can move with surprising speed to defend their young or when approached too closely by people.
Bison breed from mid-July to mid-August, and bear one calf in April and May.
Some wolf predation of bison is documented in Canada and has recently been observed in Yellowstone.
Bison live an average lifespan of 20–25 years in the wild.
Yellowstone is the only place in the lower 48 states where a population of wild American bison has persisted since prehistoric times, although fewer than 50 native bison remained there in 1902.
Fearing extinction, the park imported 21 bison from two privately owned herds, as foundation stock for a bison ranching project that spanned 50 years at the Lamar Buffalo Ranch in Yellowstone's Lamar Valley.
Activities there included irrigation, hay-feeding, roundups, culling, and predator control, to artificially ensure herd survival.
By the 1920s, some intermingling of the introduced and wild bison had begun.
With protection from poaching, the native and transplanted populations increased.
In 1936, bison were transplanted to historic habitats in the Firehole River and Hayden Valley.
In 2003, the entire population numbered 1,477.
Bison were trapped and herds periodically reduced until 1967, when only 397 bison were counted parkwide.
All bison herd reduction activities were phased out after 1966, again allowing natural ecological processes to determine bison numbers and distribution.
Presently, the park's bison population is estimated at about 4,000.
Bison are nomadic grazers, wandering high on Yellowstone's grassy plateaus in summer.
Despite their slow gait, bison are surprisingly fast for animals that weigh more than half a ton.
In winter, they use their large heads like a plow to push aside snow and find winter food.
In the park interior where snows are deep, they winter in thermally influenced areas and around the geyser basins.
Bison also move to winter range in the northern part of Yellowstone. 
The Henry Mountain bison herd is considered to be genetically pure, meaning that there is no evidence of significant hybridization between these bison and cattle.
This genetic purity appears to be different from the Antelope Island bison herd, also managed by the State of Utah.
In the Antelope Island bison herd, there now appear to be some cattle genes present.
Officially, the "American Buffalo" is classified by the United States Government as a type of cattle, and the government allows private herds to be managed as such.
This is a reflection of the characteristics that bison share with cattle.
Though the American bison ("Bison bison") is not only a separate species, but actually in a separate genus from domestic cattle ("Bos primigenius"), they clearly have a lot of genetic compatibility and American bison can interbreed freely with cattle.
Moreover, when they do interbreed, the crossbreeds tend to look very much like purebred Bison, so appearance is completely unreliable as a means of determining what is a purebred bison and what is a crossbred cow.
Many ranchers have deliberately cross bred their cattle with bison, and it would also be expected that there could be some natural hybridization in areas where cattle and bison occur in the same range.
Since cattle and bison eat similar food and tolerate similar conditions, they have often been in the same range together in the past, and opportunity for cross breeding may sometimes have been common.
In recent decades tests were developed to determine the source of mitochondrial DNA in cattle and bison, and it was found that most private 'buffalo' herds were actually cross bred with cattle, and even most state and federal buffalo herds had some cattle DNA.
With the advent of nuclear microsatellite DNA testing, the number of herds that contained cattle genes has increased.
Though approximately 500,000 bison exist on private ranches and in public herds, some people estimate that perhaps only 15,000 to 25,000 of these bison are pure and are not actually bison-cattle hybrids.
"DNA from domestic cattle (Bos taurus) has been detected in nearly all bison herds examined to date."
Significant public bison herds that do not appear to have hybridized domestic cattle genes are the Yellowstone Park bison herd, the Henry Mountains bison herd which was started with bison taken from Yellowstone Park, the Wind Cave bison herd and the Wood Buffalo National Park bison herd and subsidiary herds started from it, in Canada.
A landmark study of bison genetics that was performed by James Derr of the Texas A&M University corroborated this.
The Derr study was undertaken in an attempt to determine what genetic problems bison might face as they repopulate former areas, and it noted that bison seem to be doing quite well, despite their apparent genetic bottleneck.
One possible explanation for this might be the small amount of domestic cattle genes that are now in most bison populations, though this isn't the only possible explanation for bison success.
In the study cattle genes were also found in small amounts throughout most herds.
"The hybridization experiments conducted by some of the owners of the five foundation herds of the late 1800s, have left a legacy of a small amount of cattle genetics in many of our existing bison herds."
He also said, "All of the state owned bison herds tested (except for possibly one) contain animals with domestic cattle mtDNA."
It appears that the one state herd that had no cattle genes was the Henry Mountains Bison Herd in the Henry Mountains of Utah.
It was originally founded with bison from the Yellowstone Park Bison Herd.
However, the extension of this herd into the Book Cliffs of Central Utah involved mixing the founders with additional bison from another source, so it is not known if the Book Cliff extension of the herd is also free of cattle hybridization.
A separate study by Wilson and Strobeck, published in Genome, was done to define the relationships between different herds of bison in the United States and Canada, and to determine whether the bison at Wood Buffalo National Park in Canada and the Yellowstone Park bison herd were possibly separate subspecies, and not Plains bison.
Some scientists had previously suggested that the Yellowstone bison were either of the "athabascae" (Wood bison) subspecies, or that they were a type of 'Mountain bison' subspecies.
It was determined by the study that the Wood Buffalo Park bison were actually cross breeds between Plains bison and Wood bison, but that their predominant genetic makeup was truly that of the expected "Wood Buffalo" (Bison bison athabascae).
However, the Yellowstone Park bison herd were pure Plains bison (Bison bison bison), and not any of the other previously suggested subspecies.
Since the Yellowstone Park herd are Plains bison, that would indicate that the Henry Mountain herd are also Plains bison.