Weld County Courthouse
Location within the U.S. state of Colorado
Colorado's location within the U.S.
|Founded||November 3, 1861|
|o Total||4,017 sq mi (10,400 km2)|
|o Land||3,987 sq mi (10,330 km2)|
|o Water||30 sq mi (80 km2) 0.7%|
| o Estimate |
|o Density||76/sq mi (29/km2)|
|Time zone||UTC-7 (Mountain)|
|o Summer (DST)||UTC-6 (MDT)|
On May 30, 1854, the Kansas-Nebraska Act created the Nebraska Territory and the Kansas Territory, divided by the Parallel 40° North (Baseline Road or County Line Road or Weld County Road 2 in the future Weld County). Present-day Weld County, Colorado, lay in the southwestern portion of the Nebraska Territory, bordering the Kansas Territory.
In July 1858, gold was discovered along the South Platte River in Arapahoe County, Kansas Territory. This discovery precipitated the Pike's Peak Gold Rush. Many residents of the mining region felt disconnected from the remote territorial governments of Kansas and Nebraska, so they voted to form their own Territory of Jefferson on October 24, 1859. The following month, the Jefferson Territorial Legislature organized 12 counties for the new territory, including St. Vrain County. St. Vrain County was named in honor of Ceran de Hault de Lassus de St. Vrain, the French trader who established the first trading post on the upper South Platte River. St. Vrain County encompassed much of what is today Weld County.
The Jefferson Territory never received federal sanction, but on February 28, 1861, U.S. President James Buchanan signed an act organizing the Territory of Colorado. On November 1, 1861, the Colorado General Assembly organized 17 counties, including Weld County, for the new Colorado Territory. Weld County was named for Lewis Ledyard Weld, a lawyer and territorial secretary. He died while serving in the Union Army during the Civil War. Until February 9, 1887, Weld County's boundaries included the area now comprising Weld County, Washington County, Logan County, Morgan County, Yuma County, Phillips County, and Sedgwick County.
Weld County was thrust into the media spotlight on the evening of November 1, 1955, when United Airlines Flight 629, a Douglas DC-6B airliner flying from Denver to Portland, Oregon, exploded in midair and crashed, killing all 44 persons on board the plane and scattering bodies, wreckage and debris over a six-square-mile area of the county. The subsequent investigation of the accident revealed that Denver resident John Gilbert Graham had secretly placed a time bomb composed of 25 sticks of dynamite in a suitcase belonging to his mother, who was a passenger on the airplane. Graham was tried and convicted of the crime, and executed in 1957.
In 2013, conservative Weld County commissioners began a campaign to secede from the State of Colorado to create a new state; a state ballot measure regarding the issue was put on the November 2013 ballot. The legality of this initiative has been questioned by local attorneys. On Nov 5th, 2013, 6 out of 11 Colorado counties voted no for secession, including Weld County. Elbert, Lincoln, Logan, Moffat, Sedgwick, and Weld counties voted no, while Cheyenne, Kit Carson, Phillips, Washington, and Yuma counties voted yes. "Weld County voters said this is an option we shouldn't pursue and we won't pursue it," said Weld County Commissioner Sean Conway, "But we will continue to look at the problems of the urban and rural divide in this state."
In 2021, a group known as "Weld County, WY" organized a petition to place a measure on the November 2021 ballot for the county to secede from Colorado to join Wyoming, due to a clash between the conservative politics of Weld County and the liberal government of Colorado. Mark Gordon, the Governor of Wyoming, said when asked about the topic, "We would love that." In response to Gordon's comment, Colorado Governor Jared Polis said, "Hands off Weld County."
According to the U.S. Census Bureau, the county has a total area of 4,017 square miles (10,400 km2), of which 3,987 square miles (10,330 km2) are land and 30 square miles (78 km2) (0.7%) are water. It is the third-largest county in Colorado by area.
Weld County lies within the relatively flat eastern portion of Colorado; the northeastern portions of the county contain the extensive Pawnee National Grassland and the Pawnee Buttes, which jut 350 feet (110 m) above the surrounding terrain and are surrounded by many small canyons and outcroppings. Along the western border, hilly areas indicate the presence of the foothills of the Rocky Mountains further west.
The county is served by two interstate highways: I-25 (US 87) runs through the southwestern corner and I-76 from the south central edge northeastward to the Morgan county border. Other major roads include US 85 and US 34, which intersect near Greeley, and State Highway 14, which runs through Ault.
As of the census of 2000, there were 180,936 people, 63,247 households, and 45,221 families residing in the county. The population density was 45 people per square mile (18/km2). There were 66,194 housing units at an average density of 17 per square mile (6/km2). The racial makeup of the county was 81.71% White, 0.56% Black or African American, 0.87% Native American, 0.83% Asian, 0.08% Pacific Islander, 13.29% from other races, and 2.65% from two or more races. 27.05% of the population were Hispanic or Latino of any race.
There were 63,247 households, out of which 37.20% had children under the age of 18 living with them, 57.60% were married couples living together, 9.40% had a female householder with no husband present, and 28.50% were non-families. 21.00% of all households were made up of individuals, and 6.90% had someone living alone who was 65 years of age or older. The average household size was 2.78 and the average family size was 3.25.
In the county, the population was spread out, with 28.20% under the age of 18, 13.20% from 18 to 24, 29.70% from 25 to 44, 20.00% from 45 to 64, and 9.00% who were 65 years of age or older. The median age was 31 years. For every 100 females there were 100.60 males. For every 100 females age 18 and over, there were 98.00 males.
The median income for a household in the county was $42,321, and the median income for a family was $49,569. Males had a median income of $35,037 versus $25,757 for females. The per capita income for the county was $18,957. About 8.00% of families and 12.50% of the population were below the poverty line, including 14.60% of those under age 18 and 8.50% of those age 65 or over.
Weld County is Colorado's leading producer of cattle, grain and sugar beets, and is the richest agricultural county in the United States east of the Rocky Mountains, and the fourth richest overall nationally. It is also becoming more important as a milk producing county, with close to half of the state's cattle.  Weld County is also an important area of oil and natural gas production in the Denver-Julesburg Basin.
? means a populated place has portions in an adjacent county or counties
Similar to the fellow Denver Metropolitan Area county of Douglas, Weld leans Republican. Except for Lyndon Johnson's 1964 landslide win over Barry Goldwater, it has not voted for a Democratic presidential candidate since 1936.