Mary C. Neff (1861-1939) was born in Ohio and died in Oakland, California. She was the wife of John W. Neff, a carpenter who worked for the Southern Pacific Railroad for over 30 years. In 1885, she wrote to Mary Baker Eddy to purchase a copy of, and ask for information about bulk orders of, Science and Health with Key to the Scriptures. In June 1898, she joined The First Church of Christ, Scientist, in Boston, Massachusetts, and was also a Christian Science practitioner, listed in the directory of The Christian Science Journal from 1900 until 1905.

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