Arba, IndianaArba is an unincorporated community in Greensfork [Township, Randolph County, Indiana|Greensfork Township], Randolph [County, Indiana|Randolph County], in the U.S. state of Indiana.HistoryArba was settled by Quakers as early as 1815. A post office was established at Arba in 1849, and remained in operation until it was discontinued in 1911.