RCA, among other things, stands for Reformed Church in America. I do not know if there ever was one in Howard. By the 20th century the reformed church had absorbed many of the earlier reformed churches initially organized by Dutch and Palatine German refugees coming to America in the 18th century.
It is a small church today with a small membership. The RCA confesses several statements of doctrine and faith, including the historic Apostles' Creed, Nicene Creed, and Athanasian Creed; the traditional Reformed Belgic Confession, the Heidelberg Catechism (with its compendium), the Canons of Dort, and the Belhar Confession. Please don't ask me what all that means. I included it because it may help you decipher your Mother's diary.
Hopefully a few of the local history buffs can tell you whether or not the RCA was in Howard in 1949.