Born in Vermont, Barlow was educated mainly in New York, completing his education at the Wesleyan Seminary. He read law in the office of a prominent attorney in Batavia, New York and was admitted to the bar in 1839. That same year he came to St. Louis and soon appointed assistant to General John Ruland, clerk of the Circuit Court of St. Louis County. Three years later he was made chief deputy to James Walsh, clerk of that court. Two years after that, the county court appointed him county clerk and recorder of deeds to fill out the unexpired term of a deceased official. In 1847 he was elected to that office. While serving as a county official, he had also been active in promoting railway and other enterprises of important to St. Louis. Then in 1853, the St. Louis & Iron Mountain Railroad Company was permanently organized and he was made its secretary and treasurer. Upon the expiration of his term as clerk and recorder he turned his entire attention to railroad affairs, becoming president of the railroad company in 1859. For seven years thereafter he remained at the head of this corporation, and was known as one of the ablest of the old-time Western railway managers. In 1868 the Iron Mountain Railroad and its franchises were sold and a reorganization of the company followed. For a few years thereafter Mr. Barlow was not officially identified with the corporation. However, in 1873, he resumed connection with it as assistant to the president. Later he became local treasurer and eventually secretary of the Iron Mountain branch after consolidation with the Missouri Pacific system. As early as 1857 he served as a member of the Board of Public Schools, and was re-elected several times. As its president he contributed greatly to the building of the public school system of St. Louis. During the years 1865-6, while a member of the Missouri Legislature, he obtained a charter for the Public School Library Association, which founded the present public library, and was its first president. In 186708 he served as a member of the Board of Water Commissioners of St. Louis, and in 1869 was elected city comptroller, serving until 1871. While acting in that capacity, he formulated the “Cole-Barlow Charter,” which was enacted by the Legislature. After the adoption of the existing “scheme and charter” he was elected a member of the first city council provided for therein and served until 1879, being chairman of the committees on ways and means, and railroads. He was originally a Whig in his political affiliations, but later joined the “Free Soil” movement, being one of the small number of Missourians who took a bold stand against the extension of slavery. He later became a supporter of the Republican party.