How Long Is the San Juan River From Start to End?

Written by Telea Dodge
Published: November 26, 2023
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Today, we’ll be looking to the southwestern United States and learning about a river that flows through many states in the region. This river, the San Juan River, is an important waterway for the region – and for the fish that live in it. This incredible river is said to contain around 15,000 fish per mile, which calls anglers from around the world to its banks. Today, we’ll learn about the length and course of the river as it flows toward its mouth. How long is the San Juan River? We’re about to find out.

How Long Is the San Juan River

Gooseneck State Park along the San Juan River

The San Juan is the muddiest river in the United States.

©Jochen Hoog, CC BY-SA 3.0, via Wikimedia Commons – License

From start to end, the San Juan River spans approximately 383 miles. This is one of the main tributaries of the Colorado River, and it flows south and east from its headwaters to its mouth. It is one of the most significant drainage basins for the Four Corners Region – a region that is situated at the meeting points of New Mexico, Utah, Colorado, and Arizona. The river flows through three of these states on its course.

The headwaters of the river rest in the San Juan Mountains in southwestern Colorado. They begin at the confluence of the east and west forks of the river at elevations above 10,000 feet. This point is in Archuleta County, Colorado in the eastern portion of the San Juan Mountains.

Course of the San Juan River

San Juan River and Farmington, New Mexico

The Animas River joins with the San Juan River in Farmington, New Mexico.

©MonaMakela/ via Getty Images

From its headwaters, the San Juan River flows southwest. It winds through the foothills of the Rocky Mountains and makes its way to the Navajo Lake Reservoir. This is just north of the New Mexico border and is created by the Navajo Dam. The river then flows west through the high desert of the Colorado Plateau. It is joined by its main tributary – the Animas River – in Farmington, New Mexico. It continues westward through the Navajo Nation in New Mexico before flowing briefly back into Colorado. Then, it enters Utah in the southeastern portion of the state. The river stays in Utah for the rest of its course. It flows through Bluff, Utah, and past the town of Mexican Hat before it drains into Lake Powell. This is how it joins the Colorado River and ends its own course.

The San Juan River Compared to Other Regional Rivers

Four Corners

The Four Corners Monument is a homage to the region, which is enriched by the San Juan watershed and drainage basin.


There are a couple of other important rivers that flow through the Four Corners region. One of them, the Mancos River, is a tributary of the San Juan River. It is an 85.4-mile-long river that begins near Mancos, Colorado. It makes its way down to its confluence with the San Juan near the Four Corners Monument in New Mexico.

Another significant river in the area is a tributary of the Colorado River. The Dolores River begins its 241-mile journey in the San Juan National Forest. It then flows through Colorado and into Utah to meet the Colorado River in Grand County, Utah.

The photo featured at the top of this post is © Nick Fox/

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About the Author

Telea Dodge is an animal enthusiast and nature fiend with a particular interest in teaching a sense of community and compassion through interactions with the world at large. Carrying a passion for wild foraging, animal behaviorism, traveling, and music, Telea spends their free time practicing their hobbies while exploring with their companion dog, Spectre.

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