As of the census of 2000, there were 49,644 people, 20,343 households, and 13,141 families residing in the city.The population density was 2,073.2 people per square mile (800.3/km²).The area was the location of several ferries that offered passage across the North Platte River in the early 1840s.In 1859, Louis Guinard built a bridge and trading post near the original ferry locations.Casper is the second largest city in the state, according to the 2010 census, with a population of 55,316. Casper is nicknamed "The Oil City" and has a long history of oil boomtown and cowboy culture, dating back to the development of the nearby Salt Creek Oil Field.In 2010, Casper was named the highest-ranked family-friendly small city in the West, and ranked eighth overall in the nation in Forbes magazine's list of "the best small cities to raise a family".Temperatures typically plummet during summer nights, with an average diurnal temperature variation approaching 35 °F (19.4 °C).
Highs reach 90 °F (32.2 °C) on 31 days per year and fail to surpass freezing on 46.
5.35% of the population were Hispanic or Latino of any race.
There were 20,343 households out of which 31.8% had children under the age of 18 living with them, 49.6% were married couples living together, 11.1% had a female householder with no husband present, and 35.4% were non-families.
The town is named "Casper", instead of "Caspar", honoring the memory of Fort Caspar and Lt.
Caspar Collins, due to a typo that occurred when the town's name was officially registered.