William H. Mumler was a 19th-century photographer best known for popularizing spirit photography—images that appeared to show deceased individuals alongside the living. Beginning in the 1860s, Mumler’s photographs captivated a public eager for proof of life beyond death, particularly in the aftermath of the American Civil War.

His work attracted both devoted believers and determined skeptics, including professional investigators and stage magicians who challenged the authenticity of his methods. Though Mumler was eventually tried for fraud and acquitted, his reputation remains controversial. Regardless of interpretation, his photographs played a significant role in the history of Spiritualism, demonstrating how emerging technologies were used to support—and question—claims of spirit communication.