He was born in Baltimore to Christian Mayer, a German who emigrated in 1784 along with a friend, Lewis Brantz. Forming a business partnership that would last for decades, Lewis Brantz and the elder Mayer engaged in trade with the East Indies and Mexico. As well, Mayer for many years served as consul general of Württemberg in the United States. In 1809, Christian Mayer had a second son, whom he named after his friend and business partner. Childless himself, Lewis Brantz would eventually name the younger Mayer as his heir. After graduating at St. Mary's College, Baltimore, Brantz Mayer sailed for the East, visiting Java, Sumatra, and China, and returned in 1828. He studied law during this long voyage, and on his return home he entered the law school of the University of Maryland and was admitted to the bar in 1829. He practiced law from 1832 until 1841, when he was appointed secretary of legation to Mexico, where he remained a year, and on his return edited for a short time the Baltimore American newspaper. Brantz Mayer was again secretary of the United States legation to Mexico in 1842 and 1843. When he returned home after his 1843 visit, he published his first work, Mexico as it Was, and as it Is, which was accused of unfairness and gave rise to animated controversy. In the winter of 1844, Mayer founded the Maryland Historical Society, the original object of which was “the collecting the scattered materials of the early history of the state, and for other collateral purposes.” In 1857, he was elected a member of the American Antiquarian Society. During the American Civil War, Mayer was an active Unionist, and in 1861 was appointed president of the Maryland Union State general committee, and did much to aid the Union cause. In 1867 he was appointed a paymaster in the United States army, a post which he resigned in 1875. He contributed to the Maryland Historical Society the Journal of Charles Carroll of Carrollton during his Mission to Canada, and Tah-gah-jute, or Logan and Captain Michael Cresap.
Works
Among his works are:
Mexico as it was and as it is completed book at Wikisource.
History of the War between Mexico and the United States
Mexico, Aztec, Spanish, and Republican
Calvert and Penn, or the Growth of Civil and Religious Liberty in the United States
Observations on Mexican History and Archeology in Smithsonian Contributions
His nephew Francis Blackwell Mayer was a noted artist. Another nephew, Alfred M. Mayer, brother of Francis, was a noted physicist. His grandniece, Mary van Kleeck, was a social worker and radical labor activist.
