There are both Union & Confederate Nurses in the series. Hence the two flags to illustrate that aspect
"Mercy Street’s Mansion House Union hospital in Alexandria, Va. vividly depicts the roles of female nurses in the Civil War. Foremost is Dorothea Dix who hired Mary Phinney and sent her to Mansion House as the head nurse representing US Government policy. Nurse Ann Hastings demonstrates the competence of a Nightingale nurse, the leading trained nurses at the start of the war. Emma Green illustrates the Southern woman who volunteered her service, ministering to the Confederate wounded. Unheralded nuns are seen serving as nursing staff providing comfort and care.
Nurses, both Union and Confederate, wrote memoirs of their experiences providing an intimate and personal look at the war from varied points of view. Mary Phinney von Olnhausen’s (1818-1902) "Adventures of an Army Nurse in Two Wars" gives a glimpse into the life of a Union nurse and was an inspiration for Mercy Street."