The basic urban structure of downtown Surabaya was completed under the colonial rule of Dutch East Indies. Examining available primary sources such as aerial photographs and cadastral maps, this paper investigates how the expansion of the native urban settlement, i.e. kampungs, took place in and around the former walled town of Surabaya during the course of the 20th century. By the end of 1920's the downtown area of the city experienced two major infrastructure developments, namely the construction of the new harbor and restructuring of existing national railways. These improvements and growth of the urban structure, nevertheless, did not directly prompt the expansion of the new kampungs because of the possible control over its irregular growth. However the areal extent of kampongs grew extensively wide within the first two decades after the independence. It is quite significant to point out that in this development, many of the kampongs occupied the territories abandoned by colonial authorities at the time of Indonesian independence, or by the private enterprises of the day when the colonial properties were requisitioned in the following decade.