The Leprosy village of  Lao Si Momo was founded in 1907 in the Batak country by the Rheinische Mission Gesellschaft. It was opened some time before 1907. See KITLV image collection 1935 no. 100736.

From the annual reports by the Civil Medical Service 1909: The Government Decision of 16 December 1907 no. 14 accorded an amount to the leprosy asylum at Lao Si Momo, in the country of the Karo-Bataks on the Eastcoast of Sumatera.At that time 132 leprosy patients had been admitted. By building some addditional houses the situation of housing improved greatly. De missionary-teacher at Kabandjahe continued to care for the asylum.

From the Sumatra-Post of 12 September 1922: in an article by von Romer this leprosy facility was mentioned. ‘On the Karo-Batak plains many cases of leprosy are found. The local population is cruel in isolating them rigorously. Since some 15 years the Leprosy colony of Lao Si Momo has been  founded and cares for some 150 patients. A Batak head of the colony has been chosen who suffers also from leprosy. The NI Government provides for a periodic medical check and for a small subsidy per inhabitant. The missionary J. van den Berg is in charge of the Colony.