North to south, Texas measures 801 miles. It once extended as far north as the 42nd parallel (same as California), into present-day Wyoming. The northern border was rolled back to its present day limit (36°30′) in the Compromise of 1850.
The topmost portion of Texas (26 counties) is called the Panhandle. The Texas Panhandle is actually part of the American Great Plains. Country music fans know that an old favorite is “Amarillo By Morning”. Amarillo is in the middle of the Panhandle.
The southern tip of Texas (4 counties) is called the Rio Grande Valley (actually a floodplain, not a real valley). The Valley, as we Texans call it, borders on Mexico, and is best known for citrus fruit. On a personal note, in the late 1920s my grandfather ran a small zoo in Harlingen, a small town in the Valley. Very few people living there today remember the Harlingen zoo. Nowadays, everyone knows the Gladys Porter Zoo in Brownsville, also in the Valley, just a few miles from Harlingen.