Alexander Romeo Horton was born in 1923 in Monrovia, Liberia. As a child Horton moved to Virginia, Liberia to pursue his education at the Ricks Institute. He later attended Booker Washington Institute, where he graduated from the eighth grade in 1937. After completing high school at College of West Africa in the 1940s, Horton entered Morehouse College in Atlanta, his father's alma mater. He then began the Business and Finance Masters program at University of Pennsylvania.

Horton is best known for founding and presiding over the Bank of Liberia, the country's first indigenous banking institution. He later served on the development board that created the African Development Bank (ADB) and the ECOWAS Fund (Economic Community of West African States), a subsidiary of ADB. In the beginning stages of the ECOWAS, Horton served as the managing director, relocating to Togo. Horton held the position of chairman on the ADB board, travelling to visit almost all African Heads of State and many western leaders, presenting African Development ideas. Liberia became a key figure in the establishment of the ADB due to Horton's efforts.

Because of the 1980s coup d'état in Liberia, Horton relocated to the U.S. The mayor of Philadelphia appointed Horton as managing director of the Philadelphia Commercial Development Corporation (PCDC), While in Pennsylvania, he served as the brainchild behind the creation of one of Philadelphia's most successful black banks, the United Bank of Philadelphia. Horton also served in the administration of Philadelphia's first African-American Mayor

He helped direct the Wharton African Entrepreneurial Project and managed the Wharton/Africa Symposium in October 1983. This event involved representatives from seventeen African countries and over one hundred American businesses and institutions interested in building stronger economic ties with Africa.

Horton was a close friend of both Rev. Jesse Jackson and Liberian President Charles Taylor, and he actually initiated the meeting between Jackson and Taylor in the late 90s.

Horton was married for 49 years to Mary Eliza Horton and had five children: Shepard, Kamah, Danlette, Renee, and Romell. He died in 2005 in Abington, Pennsylvania.