By 1900, as a result of the Dawes Act and the Curtis Act, about one-half of land previously owned by Indian tribes was owned by whites.
The Wichita Mountains Wildlife Refuge was founded in 1901.
After Petitioning congress to hand over jurisdiction, the 57 acres was given to Arkansas in 1905.
In 1905, the Sequoyah Statehood Convention laid the groundwork for the Oklahoma Statehood Convention.
On June 16, 1906, Congress enacted a statute authorizing the people of the Oklahoma and Indian Territories to form a constitution and state government in order to be admitted as a state.
On November 16, 1907, President Theodore Roosevelt issued Presidential Proclamation no. 780, establishing Oklahoma as the 46th state in the Union.
In 1907 Oklahoma acquired the territory upon gaining statehood.
On November 11, 1911, the temperature in Oklahoma City reached 83 °F (28 °C), then dropped to 17 °F (−8 °C) by midnight.
In 1912, Oklahoma experienced a tornado outbreak due to a warm front traveling along a stalled cold front.
Social tensions were exacerbated by the revival of the Ku Klux Klan after 1915.
In late September 1918, the first cases of the Spanish flu appeared in Oklahoma.
In 1919, the Spanish Flu pandemic ebbed in Oklahoma, after approximately 100,000 people fell ill with the disease.
Oklahoma's population was 2,028,283 according to the 1920 U.S. census.
In 1921, the Tulsa race massacre broke out, with White mobs attacking Black people and carrying out a pogrom in Greenwood.
In 1927, Oklahoman businessman Cyrus Avery, known as the "Father of Route 66", began the campaign to create U.S. Route 66.
1934 featured weeks on end of virtual rainlessness and highs well over 100 °F (38 °C) leading to drought conditions.
In 1939, John Steinbeck's novel "The Grapes of Wrath" was published, popularizing the negative stereotype of "Okies" as uneducated, poverty-stricken Dust Bowl-era farmers.
In 1940, 90.1% of Oklahoma's population was non-Hispanic White.
In 1949, broadcast television in Oklahoma began when KFOR-TV in Oklahoma City and KOTV-TV in Tulsa started broadcasting.
Over a twenty-year period ending in 1950, Oklahoma saw its only historical decline in population, dropping 6.9 percent as impoverished families migrated out of the state after the Dust Bowl.
In 1953, Ridge Bond and the cast of "Oklahoma!" were featured on a CBS Omnibus television broadcast.
1954 featured weeks on end of virtual rainlessness and highs well over 100 °F (38 °C) leading to drought conditions.
In 1962, Yvonne Chouteau and Miguel Terekhov founded the University of Oklahoma's dance program, the first fully accredited program of its kind in the United States.
In 1976, the Medieval Fair of Norman was first held on the south oval of the University of Oklahoma campus, marking the beginning of Oklahoma's first medieval fair.
1980 featured weeks on end of virtual rainlessness and highs well over 100 °F (38 °C) leading to drought conditions.
Between 1980 and 2014, male life expectancy in Oklahoma increased by 4.0 years, while female life expectancy increased by 1.0 years.
The 1985 US Supreme Court Case Oklahoma v. Arkansas decided the land would remain Arkansas, even though the Choctaw had not been notified or asked about the territory being handed over.
In 1987, the first Oklahoma City Pride Parade was held in the gay district on 39th and Penn, and it has been an annual event in late June since.
In 1990, 81% of Oklahoma's population was White.
On April 19, 1995, the Oklahoma City bombing occurred, resulting in 168 deaths.
Between 2000 and 2010, the leading cities in population growth were Blanchard (172.4%), Elgin (78.2%), Jenks (77.0%), Piedmont (56.7%), Bixby (56.6%), and Owasso (56.3%).
In 2000, Oklahoma ranked 45th in physicians per capita.
On June 11, 2001, Timothy McVeigh was executed by the federal government for his role in the Oklahoma City bombing.
In 2001, Southern Hills Country Club hosted a U.S. Open.
In 2003, the Medieval Fair of Norman moved to Reaves Park due to its increasing size.
In 2004, data was collected that would later be used in the 2006 Catalogue for Philanthropy which ranked Oklahomans 7th in the nation for overall generosity.
In 2005, Oklahoma was the 21st-largest recipient of federal medical funding, totaling $75,801,364, with immunizations, bioterrorism preparedness, and health education as the top three funded items.
In 2005, nearly 25 percent of Oklahomans between the ages of 18 and 64 did not have health insurance, the fifth-highest rate in the nation.
In 2005, the Cherokee Nation launched a ten-year plan to increase the number of Cherokee language speakers by growing new speakers from childhood and encouraging exclusive use of the language at home. The plan aimed for 80% fluency within fifty years.
In 2011, approximately 5% of Oklahoma's residents were born outside the United States, according to U.S. Census Bureau data from 2005 to 2009.
In 2006, Tulsa's Oktoberfest was named one of the top 10 in the world by USA Today.
In 2006, the Catalogue for Philanthropy (using 2004 data) ranked Oklahomans 7th in the nation for overall generosity, associating residents with Southern hospitality.
In 2006, there were more than 220 newspapers in Oklahoma, including 177 with weekly publications and 48 with daily publications.
On November 16, 2007, Oklahoma celebrated the 100th anniversary of its statehood as part of a larger centennial celebration, which was named the top event in the United States by the American Bus Association.
In 2007, Oklahoma ranked last among the 50 states in a study by the Commonwealth Fund on health care performance.
In 2007, Tulsa's Mayfest festival entertained more than 375,000 people in four days.
In 2011, approximately 5% of Oklahoma's residents were born outside the United States, according to U.S. Census Bureau data from 2005 to 2009.
According to the 2010 census, 72.2% of Oklahoma's population was White, 8.6% were American Indian and Alaska Native, 7.4% Black or African American, 1.7% Asian, 0.1% Native Hawaiian and other Pacific Islander, 4.1% from some other race and 5.9% of two or more races; 8.9% of Oklahoma's population were of Hispanic, Latino, or Spanish origin.
At the 2010 census, Oklahoma's population was 3,751,675.
Between 2010 and 2014 125,989 Oklahomans were documented to have lived with at least one undocumented family member.
In 2010, Oklahoma had 598 incorporated places, including four cities over 100,000 in population and 43 over 10,000.
In 2010, Oklahoma's football program ranked 12th in attendance among American colleges, averaging 84,738 people at home games.
In 2010, Oklahoma's largest cities in descending order of population were: Oklahoma City, Tulsa, Norman, Broken Arrow, Lawton, Edmond, Moore, Midwest City, Enid, and Stillwater.
In 2010, the Tulsa Shock of the Women's National Basketball Association (WNBA) began playing in Oklahoma.
In 2010, the center of population of Oklahoma was in Lincoln County near the town of Sparks.
2011 featured weeks on end of virtual rainlessness and highs well over 100 °F (38 °C) leading to drought conditions.
In 2011, approximately 5% of Oklahoma's residents were born outside the United States, according to U.S. Census Bureau data from 2005 to 2009.
Between 2010 and 2014 125,989 Oklahomans were documented to have lived with at least one undocumented family member.
In 2014, males in Oklahoma had an average life expectancy of 73.7 years, and females had an average life expectancy of 78.5 years, both below the national averages.
In 2014, the Oklahoma City Blue, of the NBA G League, relocated to Oklahoma City from Tulsa, where they were formerly known as the Tulsa 66ers.
In 2015, the Tulsa Shock relocated to Dallas–Fort Worth and became the Dallas Wings.
On May 31, 2016, several cities experienced record setting flooding.
Using 2016-2018 data, the Robert Wood Johnson Foundation calculated that life expectancy (all sexes) for Oklahoma counties ranged from 71.2 years for Okfuskee County.
On June 26, 2018, Oklahoma legalized marijuana for medical purposes, becoming one of the most conservative states to approve it.
In 2018, approximately 236,882 immigrants resided in Oklahoma, making up 6% of the state's population.
Using 2016-2018 data, the Robert Wood Johnson Foundation calculated that life expectancy (all sexes) for Oklahoma counties ranged to 79.7 years for Cimarron and Logan counties.
On July 9, 2020, the Supreme Court of the United States determined in McGirt v. Oklahoma that the reservations of the Five Tribes, comprising much of Eastern Oklahoma, were never disestablished by Congress.
From 2020-2023 the Covid pandemic affected the state of Oklahoma.
In 2020, 75.5% of Oklahoma's population was White, 11.9% Hispanic or Latino of any race, 16% American Indian and Alaska Native, 9.7% Black or African American, 3.1% Asian, 0.4% Native Hawaiian and other Pacific Islander, and 9% some other race.
In 2020, ESPN called Oklahoma City "the center of the softball universe".
In 2020, according to the U.S. census, 14.2 percent of Oklahomans identified as American Indians, which is the highest indigenous population by percentage in any state.
Oklahoma City, the state's capital and largest city, had the largest metropolitan area in the state in 2020, with 1,425,695 people.
As of December 22, 2022, Oklahoma has been impacted more by the Covid pandemic (2020–2023) than the average U.S. state with 405 deaths per 100,000 population and 59% of the population fully vaccinated.
A 2022 American Community Survey estimate found that Oklahoma's population had surpassed 4 million residents for the first time.
According to HUD's 2022 Annual Homeless Assessment Report, there were an estimated 3,754 homeless people in Oklahoma.
In 2022, Southern Hills Country Club in Tulsa hosted a PGA Championship.
From 2020-2023 the Covid pandemic affected the state of Oklahoma.
As of 2024, Oklahoma had more than 4,700 dams, about 20% of all dams in the U.S.
From June 14–16, 2024, a teqball competition was held in Tulsa.
In 2028, Devon Park in Oklahoma City will host softball at the Summer Olympics, and the Riversport OKC complex will host canoe slalom.