On May 1, 1930, two toll bridges over the Canadian River were purchased for $140,000 and opened as free bridges. The Bridgeport Bridge and the Ada-Konawa Bridge.
On May 1, 1958, Pawnee County was transferred to Highway Department Division Eight and Creek County transferred to Division Four.
On May 1, 1973, the Department of Highways began construction on its new building at 200 N.E. 21st St. The total cost of building was $7,604,000.
On May 1, 1995, the Transportation Commission approved the US-70 Bypass and US-259 Bypass in Idabell.
On May 2, 1955, the Highway Commission instructed the Department to begin surveying for a location for a county maintenance headquarters in each county.
On May 3, 1948, the Highway Commission approved the designation of SH 51A from the junction of SH 51 east to Southard.
On May 3, 1982, the Transportation Department and its partners began negotiating with the Rock Island Railroad for the purchase and resumption of rail freight service from Salina, Kansas through Oklahoma to Dallas.
On May 4, 1953, the Transportation Commission approved the designation of SH-98 from Valliant to Wright City.
On May 4, 2006, Joint Resolution 55 was filed celebrating the 50th Anniversary of the federal interstate system of highways.
On May 5, 1936, the first inventory of all roads in Blaine County was completed in preparation for the first Blaine County ,General Highway and Transportation Map.
On May 6, 1974, the Commission approved a resolution stating the Urban System Program would be administered the same manner as the Federal-aid Secondary Program
On May 7, 1947, the Commission approved a resolution stating a contractor violating a contract by using faulty or inferior material would be taken into full consideration in future project bids.
On May 7, 1962, the Highway Commission approved the designation of the SH-56 Loop connecting US-75 and US-62 on the northeast bypass route in Okmulgee.
On May 7, 1984, the Transportation Commission approved a round of new construction projects following increases in the state and federal fuel taxes.
On May 8, 1935, House Bill 125 was approved authorizing the Highway Commission to use State Highway funds to purchase five bridges over the Red River.
On May 8, 1935, House Bill 275 was approved authorizing the use of safety glass in state owned motor vehicles.
On May 8, 1995, the Departmentís Ardmore Residency Building was destroyed by a tornado. Approval to build a new building was given in September 1996.
On May 9, 1936, the US-66 bridge over the Verdigris River (now the southbound SH-66 bridge over Bird Creek) was completed near Catoosa for $132,915.57.
On May 10, 1932, State Highway Commission Chairman Sam R. Hanks announced the proposed Northwest Highway, between Oklahoma City to Guymon, would be built.
On May 10, 1939, House Bill 497 was approved designation the State Capitol Building grounds, street and roads as part of the State Highway System.
On May 10, 1943, flood hit eastern Oklahoma causing an estimated $1 million in damages to roads and bridges on the highway system.
On May 10,1971, staff from the Governorís office appeared before the Commission to discuss the 1971 Summer Youth Opportunity Program for disadvantaged youths, and to recommend participation in the program.
On May 11, 1942, the last W.P.A. project awarded in Oklahoma, widening US-183 in the city of Clinton, completed
On May 12, 1969, two I-40 construction projects in Muskogee were awarded. They included 6 miles of roadway, 6 highway overpasses, 4 bridges, 2 rail overpasses and 1 highway underpass.
On May 13, 1936, the first inventory of all road in Payne County was compelted in preparation for the first Payne County - General Highway and Transportation Map
On May 14, 1935, Van T. Moon became the fourteenth Chief Engineer of the Highway Department
On May 15, 1938, the Canadian River Bridge between Lexington and Purcell was completed.
On May 15, 1957, the Cimarron River overflowed its banks flooding parts of western and northern Oklahoma following three days of heavy rain.
On May 15, 1989, Gov. Bellmon vetoed House Joint Resolution 1034 which would have renamed 11 highways and bridges after current and past legislators.
On May 16, 1957, Gov. Gary asked for Federal Aid disaster assistance following three days of flooding in western and northern Oklahoma.
On May 16, 1957, four bridges, including the newly completed Raymond Gary bridge on US 281 across the Cimarron River were destroyed by flood water.
On May 16, 1973, the I-40 realignment project from the McIntosh Co. line and extending east 6 mile was completed in Muskogee.
On May 17, 1957, Highway Director C. A. Stoldt estimated that nearly $5 million in damage had occurred on the state highway system following heavy floods in the state.
On May 18, 1943, floods hit northeastern Oklahoma for the second time within a week, closing 26 highways.
On May18, 1948, the Highway Commission approved a proposal for the City of Tulsa to furnish right-of-way and the Department pay for the construction to widen US-66 through Tulsa.
On May 18, 1958, the first segment of interstate in Oklahoma under the Federal Interstate Act of 1956 was completed on I-35 in northern Kay County.
On May 18, 1962, the Tinker Diagonal Expressway (I-40 from I-35 to Douglas Blvd.) was dedicated.
On May 18, 1998, House Bill 2238 was approved requiring ODOT to make certain improvements to roads and bridges before removing them from the State Highway System.
On May 19, 1957, Federal disaster relief officials met with Gov. Gary and state official to discuss funding to repair flood damage from the States most disastrous flooding ever.
On May 20, 1943, flooding hit Eastern Oklahoma for the second time in ten days. Nearly all bridges over the areas three rivers were washed out or severely damaged
On May 21, 1936, the Highway Commission designated SH-67 from US-75 in Mounds northeast to US-64 in Bixby.
On May 21, 1936, the first inventory of all roads in Okfuskee County was completed and work began to prepare the first Okfuskee County highway and transportation map.
On May 21, 1947, the Highway Commission approved and adopted the first official Oklahoma Department of Highways Rules and Regulations
On May 21, 1957, Gov. Gary signed a temporary 1-cent gasoline tax to pay for flood damages. The tax was set to last for seven months or until the Governor ended it.
In 1961 the week of May 21-27 was proclaimed by the Governor as National Highway Week.
On May 22, 1936, the first inventory of all roads in Wagoner County was completed and work began on the first Wagoner County General Highway and Transportation Map
On May 23, 1969, the first section of the I-40 Elk City Bypass was completed. It consisted of five highway overpasses and two railroad overpasses.
On May 24, 1944, the highway commission designated SH-75A from the junction of US 69 & US 75 in Colbert west to Cartwright.
On May 25, 1936, the first inventory of all roads in Seminole and Tulsa Counties were completed.
On May 26, 1988, the Oklahoma City Chamber of Commerce passed a resolution recommending that Interstate 235 be name the Centennial Expressway.
On May 26, 2002, the I-40 bridge over the Arkansas River near Webbers Falls was hit by two river barges and knocked down. Fourteen people were killed.
On May 26, 2003, a dedication ceremony was held for the Webbers Falls I-40 Bridge Memorial.
On May 27, 1950, a reconstructed section of US-69 between Caddo in Bryan County and Tushka in Atoka was opened to traffic.
On May 27, 1957, Gov. Gary directing the Highway Commission and the State Highway Department to devote all facilities and personnel to repairing flood damages in order to restore the roads to normal use.
On May 28, 1976, the Commission authorized the Highway Department to contract with consulting firm Modjeski and Masters to perform an independent and unbiased investigation into the cause of the US-75 bridge collapse north of Calvin.
On May 29, 1934, Construction completed on the Sh-34 bridge over the Salt Fork of the Red River south of Mangum.
On May 30, 1975, the final segment of I-40, from Texas to east of Erick, was completed, making Oklahoma one of the first states in the nation to complete its rural highway system.
In May 1925, the Department of Highways took over the maintenance on the entire State Highway System, purchasing all equipment and maintaining the state highways with no expense to the counties.
In May 1951, floods in Western Oklahoma, washed out the US-183 bridge over Beaver River in Woodward County and the US-66 bridge over the North Fork of the Red River south of Sayre