Wellington was first surveyed in 1871 and named for the Duke of Wellington. It was designated as the permanent seat of Sumner County in 1872, winning out over competitor Sumner City. Trading with the cattle herds coming up the Chisholm Trail was an important factor in the early economy of the town. The first post office in Wellington was established in July 1871. In 1887, the Chicago, Kansas and Nebraska Railway built a branch line north-south from Herington through Wellington to Caldwell. It foreclosed in 1891 and was taken over by Chicago, Rock Island and Pacific Railway, which shut down in 1980 and reorganized as Oklahoma, Kansas and Texas Railroad, merged in 1988 with Missouri Pacific Railroad, merged in 1997 with Union Pacific Railroad. Most locals still refer to this railroad as the "Rock Island".

Wellington is located at 37°16′2″N 97°24′0″W (37.267289, -97.400061), at an elevation of 1230 feet. According to the United States Census Bureau, the city has a total area of 8.19 square miles (21.21 km2), of which, 7.61 square miles (19.71 km2) is land and 0.58 square miles (1.50 km2) is water.

The climate in this area is characterized by hot, humid summers and generally mild to cool winters. According to the Köppen Climate Classification system, Wellington has a humid subtropical climate, abbreviated "Cfa" on climate maps.

Aviation Fest Kansas Wheat Festival

Chisholm Trail Museum Wellington Lake The Wellington Golf Club

As of the census of 2010, there were 8,172 people, 3,246 households, and 2,105 families residing in the city. The population density was 1,073.9 inhabitants per square mile (414.6/km2). There were 3,736 housing units at an average density of 490.9 per square mile (189.5/km2). The racial makeup of the city was 91.0% White, 1.7% African American, 1.5% Native American, 0.3% Asian, 2.0% from other races, and 3.5% from two or more races. Hispanic or Latino of any race were 8.3% of the population. There were 3,246 households of which 33.2% had children under the age of 18 living with them, 47.0% were married couples living together, 12.1% had a female householder with no husband present, 5.7% had a male householder with no wife present, and 35.2% were non-families. 30.6% of all households were made up of individuals and 14% had someone living alone who was 65 years of age or older. The average household size was 2.44 and the average family size was 3.03. The median age in the city was 37.7 years. 27.2% of residents were under the age of 18; 7.3% were between the ages of 18 and 24; 23.2% were from 25 to 44; 26.1% were from 45 to 64; and 16.1% were 65 years of age or older. The gender makeup of the city was 48.7% male and 51.3% female.

As of the census of 2000, there were 8,647 people, 3,422 households, and 2,306 families residing in the city. The population density was 1,529.6 people per square mile (590.9/km²). There were 3,795 housing units at an average density of 671.3 per square mile (259.3/km²). The racial makeup of the city was 92.36% White, 1.71% African American, 1.24% Native American, 0.29% Asian, 0.10% Pacific Islander, 2.58% from other races, and 1.72% from two or more races. Hispanic or Latino of any race were 7.26% of the population. There were 3,422 households out of which 32.9% had children under the age of 18 living with them, 53.1% were married couples living together, 9.9% had a female householder with no husband present, and 32.6% were non-families. 29.4% of all households were made up of individuals and 14.4% had someone living alone who was 65 years of age or older. The average household size was 2.47 and the average family size was 3.05. In the city, the population was spread out with 27.6% under the age of 18, 9.0% from 18 to 24, 25.6% from 25 to 44, 20.9% from 45 to 64, and 16.9% who were 65 years of age or older. The median age was 37 years. For every 100 females, there were 93.6 males. For every 100 females age 18 and over, there were 90.7 males. The median income for a household in the city was $35,410, and the median income for a family was $43,493. Males had a median income of $34,368 versus $22,254 for females. The per capita income for the city was $16,790. About 8.9% of families and 11.5% of the population were below the poverty line, including 13.6% of those under age 18 and 7.3% of those age 65 or over.

This area produces vast quantities of winter wheat and wheat is still the driving force behind the local economy, so much so that Wellington is called the "Wheat Capital of the World". Railroads and petroleum are also significant, and manufacturing, especially aircraft parts, is growing.

Ernie Barrett, Professional basketball player for the Boston Celtics (first round 7th pick in 1951 NBA draft). Also nicknamed "Mr. K-State" for his love of Kansas State and his performance as a player at Kansas State. He has a statute standing outside of Bramlage Coliseum, as well as his jersey retired. Barrett was the point guard for Wellington during their only basketball state championship in 1947. Ryleigh Buck, softball player on the United States women's national baseball team at the 2015 Pan American games in Toronto, Canada they won gold. Buck currently plays softball at Wichita State University. She graduated from Wellington in 2016. David Carradine, American actor and film director lived in Wellington for around a year in the early 1980's while filming his movie, Americana (film) in Drury, Kansas. While in Wellington, Carradine lived with his brother Robert Carradine and Dan Haggerty, also known as Grizzly Adams. Haggerty appeared in the film Arthur S. Champeny, United States Army officer Mardie Cornejo, major league baseball player for the New York Mets. Nate Cornejo, major league baseball player for the Detroit Tigers. First round draft pick. Neil Frank, meteorologist and former director of the National Hurricane Center Pawnee Bill, named Gordon William Lillie, a showman who specialized in Wild West shows and is most known for his partnership with Buffalo Bill. Pawnee Bill moved to Wellington when he was young from Illinois and was raised here. Joseph E. Maddy, pioneering music educator and founder of the Interlochen Arts Camp Chuck Miller, pop and jazz musician Kate Pelham Newcomb, physician John Travis Nixon, newspaper publisher in Monroe and Crowley, Louisiana; formerly resided in Wellington in early 1880s David L. Payne, American soldier and pioneer Tyler Ybarra, Baseball player for the Toronto Blue Jays and Colorado Rockies. Ybarra graduated from Wellington High School in 2008 and currently resides there.