MacCauley was admired for his bravery during the Civil War as one of the 75,000 soldiers who fought for the union.

Clay also made lasting impacts as a Unitarian minister all around the United States including Detroit, Washington DC, and New York.

[2] In 1859 he enrolled in Dickinson College as a sophomore, but left in 1860 after hearing Abraham Lincoln speak about patriotism and attempted to enlist in the military.

In the end, the Presbytery of Chicago decided to grant Clay MacCauley a preaching license.

When MacCauley's beliefs on specific subjects, such the atonement, changed, he was subsequently denied ordination.

Prior to being ordained as a Unitarian minister in Rochester, New York, MacCauley spent six months preaching in Detroit.

For the Smithsonian Institute's Bureau of American Ethnology, he devoted a significant amount of time to researching the Seminole Indians in Florida.

One of the mission's representatives for the Unitarian faith, Clay MacCauley, was dispatched to Tokyo.

[1] The Senshin Sakuin School for Advanced Learning was led by Clay MacCauley.

The study of religion, ethics, and social science from a scientific and philosophical perspective was the school's main focus.

In contrast to other missionary activities at the time, the Unitarian movement in Japan was unique.

Clay MacCauley served as the lone American member of the Unitarian mission in Japan for a considerable amount of time.

Upon his return to the United States, MacCauley frequently discussed Japan and made an effort to inform Americans about the country.