Historically, American bison were widespread in North America from Alaska and western California across the United States and into northern New Mexico. Today, American bison occur in geographically isolated populations in parks and preserves, other public lands, and on private ranches. The only large herds of American bison in North America are in Yellowstone National Park, Montana and Wyoming, Wood Buffalo National Park, Alberta, and Mackenzie Bison Sanctuary and the Slave River Lowlands, Northwest Territories. Smaller herds occur in Alaska;
Breeding
Breeding season - Female American bison are seasonally polyestrous, with a cycle of approximately 3 weeks' duration. The breeding season for American bison generally occurs between July and October. However, it varies in length depending on herd location.
Age at sexual maturity - Sexual maturity most commonly occurs at 2 to 4 years of age. However, some females breed as yearlings. Bulls attain sexual maturity well in advance of becoming part of the active breeding population.
Gestation and calving season - The gestation period for American bison is 9 to 9.5 months. In most regions, the calving season is generally from mid-April to May with births concentrated from the end of April through the first 2 weeks of May.
Number of young - Females generally give birth to one calf; twins are rare. American bison generally produce two calves every 3 years.
Longevity - In the wild few American bison survive more than 20 years, although there are records of cows surviving at least 40 years. In wild populations, by the time a American bison has reached age 15 it can be considered old. In captivity, lifespan increases.
American bison thrive in open grasslands, meadows, and parklands.
When available, American bison use forested areas for shade and to escape insects. Most American bison are seasonally migratory; movements are both directional and altitudinal in some regions. During historical times, large herds of American bison commonly moved southward 200 miles (322 km) or more to winter range.