In 1825 he immigrated to Texas, where he was appointed alcalde of Stephen F. Austin's colony. In 1835 he was acting jefe político of the Department of the Brazos. He was a delegate from San Felipe de Austin to the conventions of 1832, 1833, and 1835. As a member of the so-called "Peace Party," Martin disavowed the actions of William B. Travis and others of the "War Party" at Anahuac and was opposed to Texas independence from Mexico; but with the coming of the Texas Revolution he signed the declaration of war against Antonio López de Santa Anna's Centralist regime, on November 7, 1835. At Bexar in December he drew a pen-and-ink sketch of Travis, the only known portrait of the man done from life. Martin raised a company that joined Sam Houston's army at Columbus.
He was promoted to major and detached to guard the crossings of the lower Brazos River, then flanked out of his position at Fort Bend when the Mexican army crossed at the site of present Richmond. Although both Houston and Secretary of War Thomas J. Rusk approved his action in falling back before superior numbers of the enemy, Martin was irate because he had been given an inadequate command-forty-six men-to observe the four fords and ferries he was responsible for holding. When he was ordered on April 13 to rejoin the main army at the Donaho plantation, he marched his force back to Houston's headquarters and relinquished his command. Subsequently, he was an outspoken opponent of Houston and his political policies. Martin saw little service for the remainder of the war, and on May 15 Rusk regretfully accepted his resignation.
After independence Martin made his home in Fort Bend County, where he was appointed chief justice of the county on December 29, 1837, and was elected to the post on September 6, 1841. He was admitted to the bar in 1838. He was elected to represent Austin, Colorado, and Fort Bend counties in Congress. At age sixty-five, he was the oldest senator in the Sixth Congress of the Republic of Texas. He died at the home of Randal Jones in the Fort Bend settlement on April 26, 1842, in the interval between sessions. Martin County is named for him.
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