Complex sentence: Baruch began his medical career as a doctor for the Confederate army and he remained in the South during Reconstruction, during which time he helped reactivate the State Medical Association and served as president of the State Board of Health.
Split into simpler sentences: Baruch began his medical career as a doctor for the Confederate army and he remained in the South during the Reconstruction Era. He helped reactivate the State Medical Association and served as president of the State Board of Health.