Early in 1837 Henderson was appointed Texas minister to England and France and was commissioned particularly to secure recognition and treaties of amity and commerce. Largely through his efforts both England and France entered into trade agreements with the republic and ultimately recognized Texas independence. While in France, Henderson met Frances Cox of Philadelphia, whom he married in London in October 1839. He returned to Texas in 1840 and set up a law office at San Augustine. In 1844 he was sent to Washington, D.C., to work with Isaac Van Zandt in negotiating a treaty of annexation with the United States. The treaty was signed on April 12, 1844, but was rejected by the United States Senate on June 8, 1844, and Henderson, over his protest, was ordered home by President Houston.
Henderson was a member of the Convention of 1845, was elected governor of Texas in November 1845, and took office in February 1846. With the declaration of the Mexican War and the organization of Texas volunteers, the governor asked permission of the legislature to take personal command of the troops in the field. He led the Second Texas Regiment at the battle of Monterrey and was appointed a commissioner to negotiate for the surrender of that city. Later he served with the temporary rank of major general of Texas volunteers in United States service from July 1846 to October 1846. After the war he resumed his duties as governor but refused to run for a second term. He returned to his private law practice in 1847. After election by the Texas legislature to the United States Senate to succeed Thomas J. Rusk, Henderson served in the Senate from November 9, 1857, until his death, on June 4, 1858. He was buried in the Congressional Cemetery, Washington. In 1930 his remains were reinterred in the State Cemetery in Austin. Henderson County, established in 1846, was named in his honor.
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Texas State Cemetery