Philadelphia financier Jay Cooke established the first modern American investment bank during the Civil War era. However, private banks had been providing investment banking functions since the beginning of the 19th century and many of these evolved into investment banks in the post-bellum era. However, the evolution of firms into investment banks did not follow a single trajectory. For example, some currency brokers such as Prime, Ward & King and John E. Thayer and Brother moved from foreign exchange operations to become private banks, taking on some investment bank functions. Other investment banks evolved from mercantile firms such as Thomas Biddle and Co. and Alexander Brothers.