The Protestant auxiliary hospital Kolongan Atas near Sonder was established by the Vereenigde Kerkgemeenten van Sonder (United church congregations) and was one of the oldest church institutions in the Minahasa, dating from 1907. The hospital was looked after by a European nurse and was visited once a week by an indigenous doctor. The capacity was 40 beds. From mid 1938 the management is entrusted to the Gouvernements Indisch Arts, see Decision Chief DVG of 27 April 1938 no. 14631/1.

Sonder was a town in the Minahasa, belonging to the subdepartment of Tondano and the Residency of Manado. The Minahasa had 310,000 inhabitants of whom 24,000 Europeans and 6,000 Chinese (Gonggryp 1934).

The hospital still exists (2018) and is now known as Rumah Sakit Umum Siloam GMIM Sonder. It is classified as a category D hospital (hospital on a district level). Its address is Kolongan Atas, Sonder. Website: siloam_sonder@yahoo.com.