Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Lesser Slave River is a river in central Alberta, Canada. It is a major tributary of the Athabasca River. The Lesser Slave Lake and the river were the main links to the Peace River district until the beginning of the 20th century, when the construction of the Northern Alberta Railway facilitated transportation in the area. The river originates from the Lesser Slave Lake at the town of Slave Lake. The average discharge at the mouth of the lake is 20 m³/s. It flows eastwards for 61 km, and merges with the Athabasca River at the village of Smith. From its headwaters of South Heart River, it has a total length of more than 280 km.