Bartlesville was officially surveyed in February 1902. Townsite lots were appraised and sold, with current occupants receiving preemption rights. Missouri, Kansas and Texas Railway (MK&T) service began in 1903. The MK&T leased track between Bartlesville and Dewey from the AT&SF and used Bartlesville's AT&SF depot. Bartlesville was selected the Washington County seat at the Constitutional Convention of 1906, and work on the county courthouse began in 1913. (The original Washington County courthouse was replaced by the present facility, a 1933 federal post office and court building, in 1972). Local businesses circa 1907 included the Great Western Glass Company, manufacturer of Oklahoma's first glass products, and numerous petroleum industry firms.

The presence of oil near Bartlesville was noticed as early as 1875. The Nellie Johnstone Number One, Oklahoma's first commercial oil well, was drilled at Bartlesville in April 1897. Profitable development of the region's oil fields began with the arrival of the AT&SF. (AT&SF tank cars first carried oil from Bartlesville to a Neodesha, Kansas, refinery in May 1900.) The Prairie Oil and Gas Company built a pipeline loading rack at the Bartlesville depot in 1900, and laid a pipeline to oil leases in present Osage County, Oklahoma. In 1903 the Prairie Oil and Gas Company built a thirty-five-thousand-gallon oil storage tank near the Bartlesville depot, and in 1904 completed a trunk pipeline—Oklahoma's first—from Bartlesville to Humboldt, Kansas.

Surrounded by oil-field activity, Bartlesville boomed. More than sixty oil companies were based there in 1909, including the Barnsdall Oil Company and the Indian Territory Illuminating Oil Company. Such notable oilmen as Frank Phillips, L. E. Phillips, Waite Phillips, Harry F. Sinclair, and a young J. Paul Getty, whose father formed the Minnehoma Oil and Gas Company, called Bartlesville home. In 1917 Frank and L. E. Phillips incorporated the Phillips Petroleum Company. From its Bartlesville headquarters the Phillips Petroleum Company became Oklahoma's largest company and was the mainstay of the local economy into the twenty-first century. Despite its 2002 merger with Conoco, Inc., and the relocation of company headquarters to Houston, Texas, ConocoPhillips remained Bartlesville's largest employer.

Oil brought other industries to Bartlesville. During the 1920s Harold C. Price, founder of the H. C. Price Company, developed an electric welding technique for oil pipeline construction. In 1956 he commissioned architect Frank Lloyd Wright to design the company's headquarters building. The result was the Price Tower, Wright's only skyscraper. The H. C. Price Company was liquidated in 1980.

A Russian immigrant, Armais Arutunoff, who invented the submergible pump, established the Bart Manufacturing Company at Bartlesville in 1928. He later changed his company's name to the REDA (an acronym for Russian Electrical Dynamo of Arutunoff) Pump Company. As president and chair of the board, Arutunoff sold his company to TRW, Inc., in 1969. TRW REDA Pump was a major manufacturer of submergible pumps used in the petroleum industry. The firm became Schlumberger-REDA Production Systems in the late 1990s.

Bartlesville had three zinc smelters—Lanyon-Starr, Bartlesville Zinc, and National Zinc—that opened in 1907. The natural gas smelters produced more than twenty-eight tons of zinc in 1909, with peak production occurring during World War I. Bartlesville Zinc purchased Lanyon-Starr in 1915 and moved to Blackwell, Oklahoma, in the 1920s, while National Zinc remained operational until 1997. Early smelter employees lived in nearby Smelter Town, Pruneville, and other communities. Many workers were Polish, including Gus Mnich, who became a well-known local grocer.

Another ethnic family that found success in Bartlesville was the Madansky (Madanic) family. Russian Jews, the Madanskys changed their name to May. Their Madansky Clothing Company, which opened at Bartlesville in 1910, is now May Brothers Department Store. It has the distinction of being Oklahoma's oldest clothing store run by the same family at the original address.

Bartlesville expanded east of the Caney River after 1950. The local population increased from 4,215 in 1907 to 6,181 in 1910. That number rose from 14,763 in 1930 to 27,878 in 1960, to 34,256 in 1990. Passenger rail service ended in April 1971. The MK&T line from Bartlesville to Coffeyville, Kansas, was acquired by the Southeast Kansas Railroad (SEKR) in 1994 and is inactive. The South Kansas and Oklahoma Railroad (SKOL) purchased the local AT&SF track in 1990 and merged with the SEKR in 2000.

 Washington County's second largest community, Dewey is situated on U.S. Highway 75, seven miles northeast of downtown Bartlesville. Dewey was founded in 1899 by Jacob H. Bartles and was named in honor of Spanish-American War hero Adm. George Dewey. The Dewey post office was established on April 19, 1899, and the town was incorporated on December 8, 1905.  In March 1875 Jacob H. Bartles, a son-in-law of Delaware Chief Charles Journeycake, purchased a grist mill on the north bank of the Caney River at present Bartlesville. He soon enlarged the mill and opened a trading post and a hotel nearby. When the Atchison, Topeka and Santa Fe Railway bypassed his settlement in 1899, Bartles relocated three miles to the north, moving his trading post intact to a wheat field he possessed near the railroad right-of-way. There he built the Dewey Hotel, which opened in 1900. 

Dewey's first newspaper, the Dewey Eagle, was published in 1900. The Missouri, Kansas and Texas Railway reached town in 1903. By 1907 the community had 748 residents. That number increased from 1,344 in 1910 to 2,095 in 1930. Wheat was an important local commodity, and the Bartlesville-Dewey Field provided petroleum industry employment. The Dewey Portland Cement Company opened in 1906 and remained a major employer until staff reductions in the 1950s. The plant closed in September 1965.

Western actor Thomas E. "Tom" Mix was a performer with the Miller Brothers 101 Wild West Show when introduced to Dewey native Olive Stokes. Mix married her in 1909, and they resided at Dewey, where he worked in law enforcement. Dewey's Tom Mix Museum opened in 1968. The museum and its collection of Mix memorabilia have been operated and maintained by the Oklahoma Historical Society since 1973. Dewey is also home to the Washington County Fairgrounds. The Dewey Roundup was held at the fairgrounds beginning in 1916. Premiering in 1909, the rodeo was an annual Fourth of July event until 1948.

Dewey's population declined from 3,545 in 1980 to 3,179 in 2000. The highest percentage of those employed in 2000 worked in sales. The Dewey public school system consists of an elementary school, a middle school, and a high school. In the tradition of the Dewey Roundup, the schools' mascot is a Bulldogger.

Vera is a rural community in southern Washington County. It is situated approximately seven miles southeast of Ramona and two miles east of U.S. Highway 75, near the intersection of County Roads E0390 and N4000. Originally known as Evans, the town was renamed Vera in November 1899 and incorporated in 1904. Vera's first mayor was Hugh Watson.

Vera's history began when William C. Rogers opened a store there in 1899. Rogers, who was elected principal chief of the Cherokee Nation in 1903, employed William and Cecilia Evans, a Welsh couple, for whom the town was first named. The Vera post office was established on December 15, 1899, with Eli Carr as postmaster. Rogers donated the land upon which the Atchison, Topeka and Santa Fe Railway depot was constructed in 1900. The town's population increased from 175 in 1907 to 312 in 1910.

Vera was a farming community whose primary crops were corn and hay. A grain elevator and hay barns lined the railroad tracks, and the Richardson Grain Company was founded by Charlie Richardson in 1905. Abundant harvests of prairie hay resulted in Vera's designation as "the Hay Capital of the World." The community experienced an oil boom in 1915. The Vera Field, located southeast of town, had twenty-five oil wells and nine gas wells by mid-October 1915. Several dairies operated near Vera during the 1930s.

Vera's first school opened in 1900. A brick school building was constructed in 1910, and a larger facility was erected in 1928-29. The Cherokee Times and the Vera Monitor were early newspapers. The latter became the Vera Record in 1913.

Improved roads and the prevalence of automobiles caused Vera's population to decline after 1920, reaching a low of 125 in 1960. The 1970 and 1980 censuses reported 215 and 185, respectively. The railroad depot and business district were gone by 1982, and only four churches, the post office, a fire station, and a convenience store remained. The town had 188 residents in 2000. At the turn of the twenty-first century children in Vera, in addition to those in Ochelata and Oglesby, attended the Caney Valley public schools in Ramona.