1963: King Kirchner and Don Bodard purchased Unit Drilling Company from Woolaroc Oil Company. At that time, Unit consisted of three rigs which engaged in the contract drilling of oil and natural gas wells.

1964: Unit purchased four rigs from Falcon Seaboard Drilling Company while continuing to build the new company.

1974: Four more rigs were purchased from Leaben Drilling Company, as the demand for Unit's services increased.

1980: The price of oil doubled and in some cases natural gas prices exceeded $9.00 per Mcf. Unit bought five rigs from Barrett Drilling Company, helping Unit to meet the demand of an unprecedented drilling boom.

1988: In early 1988, as a result of its diversifying business activity, Unit reorganized its business operation resulting in its oil and natural gas exploration operations being carried out by its wholly owned subsidiary, Unit Petroleum Company and its contract drilling service being conducted by its wholly owned subsidiary, Unit Drilling Company.

1997: Unit purchased Hickman Drilling Company, a privately-owned western Oklahoma and Texas panhandle contract drilling company. With this acquisition and the purchase of an additional rig, Unit increased its rig fleet by ten, bringing the total fleet to 34 rigs.

1999: Unit completed a public offering of 7,000,000 shares of common stock and received net proceeds of $50.4 million. Unit used $40.0 million of the proceeds to pay the cash portion of an acquisition completed on September 30, 1999. Unit acquired substantially all of Parker Drilling Company's U.S. lower 48 domestic onshore drilling assets, which included 13 diesel-electric deep drilling rigs. The acquisition increased Unit's onshore drilling rig fleet to 47 rigs and opened up a new market for the Company in the Rocky Mountains.

2001: In the first half of 2001, Unit Drilling added five rigs to its land fleet increasing the fleet to a total of 55 rigs.

2002: In August of 2002, Unit Drilling purchased 20 drilling rigs from Cactus Drilling Company, increasing the fleet to a total of 75 rigs. Twelve of the acquired rigs are SCR electric.

2003: The acquisition of SerDrilco, Inc. was completed. With this acquisition, Unit added 12 drilling rigs, a fleet of 12 trucks and a district office in Borger, Texas.

2004: In August of 2004, Unit completed the acquisition of Sauer Drilling Company, a Casper, Wyoming-based drilling company. The acquisition included 9 drilling rigs, a fleet of trucks, and an equipment and repair yard with associated inventory, located in Casper.

2005: In January of 2005, Unit closed its acquisition of a subsidiary of Strata Drilling LLC. Unit acquired two drilling rigs, as well as spare parts, inventory, drill pipe, and other major rig components.
In August, Unit closed its acquisition of all the Texas drilling operations of Texas Wyoming Drilling, Inc. The acquisition included 7 drilling rigs.

2006: Six rigs were constructed during 2006, two for the Mid-Continent operations and four for the Rocky Mountain operations. One rig was lost during the year from a well control situation. The rig fleet numbered 117 rigs at year end.

2007:  In June, Unit completed the acquisition of a privately owned drilling company operating primarily in the Texas Panhandle. The acquired company owned nine drilling rigs ranging from 800 to 1000 horsepower, a fleet of 11 trucks, and an office, shop and equipment yard.

Unit also constructed three new 1500 horsepower diesel electric/SCR drilling rigs during the year. Two of the rigs were for the Rocky Mountain operations and one for the Mid-Continent operations. The rig fleet totaled 129 rigs at year end.

2008: Unit constructed three new 1500 horsepower diesel electric/SCR drilling rigs during the year for the Rocky Mountain operations. The rig fleet totaled 132 rigs at year end.

2010:  Unit announced the sale of eight of its idle mechanical drilling rigs to an unaffiliated third party.  These rigs range in horsepower from 800 to 1,000.  Proceeds from the sale will be used to refurbish and upgrade certain rigs to gear them toward horizontal drilling activity.  At the close of the sale, the number of rigs in the fleet totaled 123.

During the third quarter, Unit conveyed 3 of its idle mechanical drilling rigs to an unaffiliated third party in exchange for a 1,200 horsepower electric rig plus cash.  The three sold rigs range in horsepower from 650 to 1,000.  At the end of this transaction the fleet totaled 121.

2011:  Unit added seven new-build drilling rigs to its fleet throughout 2011.  All seven of these drilling rigs are 1,500 horsepower, have 2 to 3-year contracts, and are deployed in the Bakken shale and Pinedale.  At the end of the year, the fleet totaled 128.

2012:  Unit added two new 1,500 horsepower drilling rigs to its fleet.  Over the last two years, Unit refurbished or upgraded 34 drilling rigs to meet customers’ demands.

2013:  During 2013, Unit finished the design for its new BOSS drilling rig, a purpose-built, 1,500 horsepower AC rig that combines the best technological innovations into a single unique rig to meet the demands of the market. 

2014:  The first BOSS drilling rig began operating during the first quarter. Two additional BOSS drilling rigs were built and placed into service during the year.

2015:  At year-end Unit removed 31 drilling rigs from its fleet that did not fit the company's projected future needs.

During the first half of 2015, Unit placed into service five new BOSS drilling rigs. Unit currently has eight BOSS drilling rigs.