The Pasig River located in southwestern Luzon, Philippines has long been viewed as the primary highway for the movement of communities and trade commodities from Manila Bay to the interior regions around Laguna de Bay in the past. While it may have served as the major channel of transport and the main reason for the emergence of important settlements in the region, the role of its tributaries are often ignored and underestimated in the study of past settlement patterns, movements, and interactions. This exploratory paper looks at the role of tributaries in understanding early movements and settlements, using least cost paths (LCP) analysis of digitized archival maps. Optimum paths among identified settlements were modelled on the riverine movement of goods and people. This study aims to explore the archaeological potentials of LCP such as site identification and interpretations.