O. S. Barr (1853-1906) was born in West Brookfield, Massachusetts, and died in Lynn, Massachusetts. Although Barr expressed an interest in studying with Mary Baker Eddy, there is no record of him studying with her or uniting with the Church. He briefly maintained a healing practice in Worcester, Massachusetts, in the mid-1880s before moving to Lynn and founding the Barr Mackintosh Company.

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