Businessman, banker, politician, and railroad promoter, Miguel Antonio Otero was born in Valenica, New Mexico (then a province of the Mexican Republic), on June 21, 1829. Otero was educated in private schools in Missouri, attended St. Louis University, and graduated from Pingree College in Fishkill, New York. He taught briefly at Pingree before returning to Missouri, where he studied law under Governor Trusten Polk. After being admitted to the bar in 1851, Otero returned to New Mexico (by then a U.S. territory) to practice law. He quickly became involved in territorial politics: he served in the territorial legislature, briefly held the position of territorial district attorney, and was elected New Mexico's delegate to Congress in 1855 (he held that position until 1861). While serving in Congress Otero married Mary Josephine Blackwood of Charleston, South Carolina; the Oteros had four children (son Miguel Antonio Jr. was New Mexico Territory's first Hispanic American governor).

Otero focused on a variety of business ventures after leaving Congress. In 1867 he opened a mercantile business in Westport Landing, Missouri, and as the railroad moved west across Kansas he relocated to Leavenworth, Fort Harker, and Hays City. Otero also became active in railroad promotion. He worked for the Atchison, Topeka, and Santa Fe Railroad during the 1870s and he helped organize the New Mexico and Southern Pacific Railroad, which built through New Mexico. At Raton Pass in December 1878, Otero drove the ceremonial spike into the first rail laid in New Mexico. By the late 1870s Otero was living in Las Vegas, New Mexico, and was engaged in mining, banking, health resorts, and a telephone company. He founded and was the first president of the San Miguel National Bank. Otero died of pneumonia at age fifty-two on May 30, 1882, in Las Vegas.