The Rio Grande, Red River and Sabine River all provide natural state lines where Texas borders Oklahoma on the north, Louisiana and Arkansas on the east, and New Mexico and the Mexican states of Chihuahua, Coahuila, Nuevo León, and Tamaulipas to the south.

Rio Grande ValleyBy residents, the state is generally divided into North Texas, East Texas, South Texas, and West Texas, but according to the Texas Almanac, Texas has four major physical regions: Gulf Coastal Plains, Interior Lowlands, Great Plains, and The Basin and Range Province. This is the difference between human geography and physical geography.

Some regions of Texas are associated with the South more than the Southwest (primarily East Texas and North Texas), while other regions share more similarities with the Southwest than the South (primarily West Texas and South Texas). The Texas Panhandle and South Plains regions don't fit either category; they seem to have more in common with parts of the Midwestern United States. The size of Texas prohibits easy categorization of the entire state wholly in any recognized region of the United States; geographic, economic, and even cultural diversity between regions of the state preclude treating Texas as a region in its own right.

On November 6, 1528, shipwrecked Spanish conquistador Álvar Núñez Cabeza de Vaca became the first known European in Texas

Prior to 1821, Texas was part of the Spanish dominions of New Spain. Moses Austin bought 200,000 acres (800 km²) of land of his choice. In 1821, Texas became part of Mexico and in 1824 became the northern section of Coahuila y Tejas. On January 3, 1823, Stephen F. Austin began a colony of 300 American families along the Brazos River. This group became known as the "Old Three Hundred." The "Conventions" of 1832 and 1833 responded to rising unrest at the policies of the ruling Mexican government.

In 1835, Antonio López de Santa Anna, President of Mexico, proclaimed a unified constitution for all Mexican territories, including Texas. North American settlers in Texas announced they intended to secede from Mexico rather than be forced to the new Mexican constitution and instead, asked for consideration under the original 1824 Mexican Constitution which allowed: freedom of religion, freedom of thought and the press and also enslavement, which Mexico had abolished under this new constitution. Other policies that irritated the Texans included the forcible disarmament of Texan settlers, and the expulsion of immigrants and legal land owners originally from the United States. The example of the Centralista forces' suppression of dissidents in Zacatecas also inspired fear of the Mexican government.

Republic of Texas. The present-day outlines of the U.S. states are superimposed on the boundaries of 1836–1845On March 2, 1836, the Convention of 1836 signed a Declaration of Independence, declaring Texas an independent nation. On April 21, 1836, the Texans won their independence when they defeated the Mexican forces of Santa Anna at the Battle of San Jacinto. A factor in the defeat of Santa Anna's army at San Jacinto was the time the Texas Army got to gather itself, thanks to a small group of defenders at The Alamo and General Sam Houston's strategy of giving up land until he had rallied an army. Santa Anna was captured and signed the Treaties of Velasco, which gave Texas firm boundaries; Mexico repudiated the treaties, considered Texas a breakaway province, and vowed to reconquer it. However, the Mexican political system was so unstable that it was never able to make good on its threats. Later in 1836, the Texans adopted a constitution that formally legalized slavery in Texas. The Republic of Texas included all the area now included in the state of Texas, and additional unoccupied territory to the west & northwest.

On December 29, 1845, Texas was admitted to the United States as a constituent state of the Union. The Mexican–American War followed, with decisive American victories. Texas grew rapidly as migrants poured into the rich cotton lands.

During the American Civil War, the Texas legislature authorized secession from the United States on February 1, 1861 and was accepted as a state by the provisional government of the Confederate States of America on March 1, 1861. Texas was most useful for supplying hardy soldiers for Confederate forces (veterans of the Mexican-American War), and in cavalry. As a whole, Texas was mainly a "supply state" for the Confederate forces until mid 1863, when the Union capture of the Mississippi River made large movements of men or cattle impossible. Texas regiments fought in every major battle throughout the war.

Immediately preceding and during World War II, existing military bases in Texas were expanded and numerous new training bases were built, especially for Naval and Military Aviation training. Many Americans and allied troops (including Free French Air Forces) came to Texas as part of the military mobilization.

From 1950 through the 1960s, Texas modernized and dramatically expanded its system of higher education. Under the leadership of Governor John B. Connally, the state produced a long-range plan for higher education, a more rational distribution of resources, and a central state apparatus that managed state institutions with greater efficiency. Because of these changes, Texas universities received federal funds for research and development during the John F. Kennedy and Lyndon B. Johnson administrations.

The executive branch consists of the Governor, Lieutenant Governor, Comptroller of Public Accounts, Land Commissioner, Attorney General, Agriculture Commissioner, the three-member Texas Railroad Commission, the State Board of Education, and the Secretary of State. The comptroller decides if expected state income is sufficient to cover the proposed state budget. Except for the secretary of state—who is appointed by the governor with the advice and consent of the Senate—each of these officials is elected (the three Railroad Commission members are voted at-large; the State Board of Education members are voted in single-member districts). There are also many state agencies and numerous boards and commissions. Partly because of many elected officials, the governor's powers are quite limited in comparison to other state governors or the U.S. President. In popular lore and belief the lieutenant governor, who heads the Senate and appoints its committees, has more power than the governor. The governor commands the state militia and can veto bills passed by the Legislature and call special sessions of the Legislature (this power is exclusive to the governor and can be exercised as often as desired). The governor also appoints members of various executive boards and fills judicial vacancies between elections.

The Legislature of Texas, like the legislature of every other state except Nebraska, is bicameral (that is, it has two chambers). The House of Representatives has 150 members, while the Senate has 31. The speaker of the house, currently Tom Craddick (R-Midland) leads the House, and the lieutenant governor (currently Republican David Dewhurst) leads the state Senate. The Legislature meets in regular session only once every two years. The Legislature cannot call itself into special session; only the governor may call a special session, and may call as many sessions as often as desired.

The judicial system of Texas has a reputation as one of the most complex in the United States, with many layers and many overlapping jurisdictions. Texas has two courts of last resort: the Texas Supreme Court, which hears civil cases, and the Texas Court of Criminal Appeals. Except in the case of some municipal benches, partisan elections choose all of the judges at all levels of the judiciary; the governor fills vacancies by appointment.

Texas remained largely rural until World War II, with cattle ranching, oil, and agriculture as its main industries. Cattle ranching (though important) was never Texas's chief industry – before the oil boom back to the period of the first Anglo settlers, the chief industry was cotton farming (as in most of the South).

In 1926, San Antonio had over 120,000 people, the largest population of any city in Texas. After World War II, Texas became increasingly industrialized. Its economy today relies largely on information technology, oil and natural gas, fuel processing, electric power, agriculture, and manufacturing. The major segment of the economy depends largely on the region involved – for example, the timber industry is a major portion of the East Texas economy but a non-factor elsewhere, while aerospace and defense manufacturing is primarily centered within the Dallas-Fort Worth Metroplex.

The state has two major economic centers: Dallas and Houston. Houston stands at the center of the petrochemical and biomedical research trades while Dallas functions as the center of the aerospace/defense manufacturing and information technology labor market in Texas. Other major cities include San Antonio, Austin, Brownsville, Lubbock, Amarillo, Abilene, Bryan-College Station, Beaumont, McAllen, Tyler, Odessa and Midland. Other important cities include Killeen (home to Fort Hood, the largest military post in the U.S.) and the cities of El Paso, Eagle Pass, and Laredo (these have particular significance due to their location on the border with Mexico, making them important trade points).

As of 2006, Texas, for the first time, has more Fortune 500 company headquarters (56) than any other state (California has 55; ironically, it was due to the move of Fluor from California to Texas). This has been attributed to both the growth in population in Texas and the rise of oil prices in 2005, which resulted in the growth in revenues of many Texas oil drilling and processing companies.

Port of HoustonTexas is the largest international exporter among the 50 American states, with international merchandise exports totaling $117.2 Billion in 2004. In 2002, the Port of Houston was 6th among the top sea ports in the world in terms of total cargo volume; Air Cargo World rated Dallas-Fort Worth International Airport as "the best air cargo airport in the world".

Texans pride themselves in a history of tradition, yet they seek new social and technological developments also. Round Rock is the headquarters of Dell and the surrounding area is known as "Silicon Hills". Dallas is a famously cosmopolitan metropolis and the birthplace of the integrated circuit, Houston is a global leader in the energy industry. The cultures of San Antonio and El Paso retain their Mexican heritage while Fort Worth maintains its western heritage.