Yes. Texas was an independent sovereign country.
From March 2, 1836, to February 19, 1845, The Republic of Texas existed as an independent country having its own flag, seal, and currency. It had a Congress and the country was headed by a President. The Republic of Texas had official recognition as a country from the United States, Great Britain, France and several other countries, many of whose ambassadors were represented here.
The boundaries of the Republic of Texas had parts of New Mexico, Kansas, Oklahoma, Colorado and Wyoming, as we know today.
How the Republic of Texas came about?
From 1684 to 1689 it was under the control of the French and known as French Texas; from 1690 to 1821 it was under Spanish control and known as Spanish Texas; from 1821 to 1836 it was under Mexican control and known as Mexican Texas.
The Mexican government invited settlers from outside to settle in Texas and many moved in to make Texas their home. Soon, disillusionment with the Mexican government brought the native Hispanic Tejano people closer to the white settlers and they rebelled against the Mexican government with frequent battles being fought.
The Texas Revolution culminated in the famous Battle at the Alamo in San Antonio, which saw 189 brave Texians, as they called themselves back then, hold out for seven days against a 4,000 strong Mexican army. Around 1,500 Mexican attackers were killed or injured before they overran the Alamo. All 189 Texians died defending the Alamo.
A month later, on April 21, 1836, the Texian army under command of General Sam Houston, took on the Mexican forces in the historic but brief Battle of San Jacinto that lasted just 18 minutes and was to be the war that won Texas its independence.
On October 3, 1836, the first Congress of the Republic of Texas assembled for the first time at Columbia and on October 22 the same year, Sam Houston was elected its first President. On March, 1, 1837, the United States officially recognized the Republic of Texas.
Between 1837 and 1845, there were several clashes between Texians and native Comanche Indians and between Texians and Mexico.
On December 29, 1845, the United States annexed the Republic of Texas. It was merged with the United States as the 28th state. On February 19, 1846, transitions of power took place from the Republic of Texas to the State of Texas.
It is interesting to note that the State of Texas holds the right to secede from the United States at any time should it so wish.
The State of Texas today
Texas covers an area of 268,579 sq miles and is home to 27,862,596 people (July 2016 est.). The state shares a 1,254 miles border with Mexico that stretches from El Paso in the west to Brownsville in the east with the Rio Grande river as the demarcation.
The per capita income is $26,999 (2015); Median household income is $53,207 (2015). Houston is the most populated city with 2,296,224 people living there, followed by San Antonio 1,469,845 and Dallas 1,300,092.