Andrew Belcher Gray, surveyor, son of William and Sarah (Scott) Gray, was born on July 6, 1820, in Norfolk, Virginia, where William Gray was the British consul. He began surveying as a teenager and helped Capt. Andrew Talcott in the survey of the Mississippi River delta. Edwin W. Moore recruited him and his brother Alfred G. Gray to the Texas Navy in 1839, but, apparently disenchanted, Andrew Gray left the navy. In 1839 and 1840 he served the Republic of Texas and Gen. Memucan Hunt in surveying the United States-Texas boundary. He also surveyed the copper-rich Keweenaw Peninsula, part of Michigan that protrudes into Lake Superior. He spent the Mexican War in North Texas and was appointed the principal surveyor of the United States-Mexican border after the Treaty of Guadalupe Hidalgo in 1848.
Work for the survey began at San Diego, California, as did the personal, professional, and political conflict that marked it. Among other disputes in the surveying party, Gray is said to have shot and wounded boundary commissioner Col. John B. Weller in San Diego. The treaty had set parameters according to Disturnell's map, but when the commission began work in Texas, Gray realized that this map was faulty and that the United States and Texas stood to lose valuable land if it were used. Particularly at stake was the area Gray considered the only practicable southern railroad route to the Pacific. John R. Bartlett, the commissioner appointed after Weller's controversial removal, had determined that the map would be followed but corrected in the process. The disagreement between Gray and Bartlett became so acrimonious that Gray was replaced by William H. Emory. Gray subsequently published his report on the Mexican boundary survey, Survey of a Route for the Southern Pacific Railroad, on the 32nd Parallel (1856).
In 1853 he was surveying again, this time for the Texas Western Railroad Company. The report features illustrations of 1850s Texas by Carl Schuchard. Gray's botanical paper "On the Ammobroma Sonorae" was published in the Proceedings of the American Association for the Advancement of Science in 1855. On June 23, 1856, Gray married Apolina Leacock of New Orleans. They had three children.
Gray entered the Confederate Army in 1861 as captain of the infantry, First Division, Western Department. As chief engineer, he fortified Island No. 10, Tennessee, in the Mississippi River. On April 16, 1862, while conducting a survey for Gen. P. G. T. Beauregard, Gray was killed at Fort Pillow.