Where Does the Rio Grande River Start?

Written by Jeff Young
Updated: January 17, 2023
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The Rio Grande stretches for nearly 1900 miles from the Colorado Rockies all the way to the Gulf of Mexico. Along the way, it forms the border between Mexico and Southwestern Texas.

It’s one of the longest rivers in North America, truly deserving of the name “Rio Grande,” which is Spanish for “big river.” In Mexico, it is also referred to as the Rio Bravo (meaning “furious river”) or Rio Grande del Norte.

Where Does the Rio Grande River Start?

Uncompahgre Peak Colorado

The Rio Grande begins its 1,896-mile journey high up in the San Juan Mountains of Colorado.


The Rio Grande begins high up in the San Juan Mountains of Colorado, in the wilderness of the Rio Grande National Forest. Even more specifically, it starts as several small streams on the eastern side of Canby Mountain, 12,000 feet above sea level.

Canby Mountain is a part of the Continental Divide—the line which separates rivers flowing to the Pacific Ocean from those flowing to the Atlantic. Rain and snowmelt on the northern and western sides of Canby Mountain flow west into the Colorado River, while water on the eastern and southern sides of the mountain drains into the Rio Grande toward the Gulf of Mexico.

How Long is the Rio Grande River?

The Rio Grande is about 1,896 miles (3,051 kilometers) long. This makes it the 4th largest river in the United States—longer than the Colorado River (1,450 miles) but shorter than the Yukon River (1,936 miles).

Globally, the Rio Grande is ranked as the 28th longest river worldwide—a little bit longer than the Lower Tunguska River in Russia (1,857 miles) and just a tiny bit shorter than the St. Lawerence-Niagara river system between Eastern Canada and the US (1,900 miles).

Approximately 1,255 miles of the Rio Grande’s 1,896-mile length forms the US-Mexico border between Texas and the Mexican states of Chihuahua, Coahuila, Nuevo León, and Tamaulipas.

Where Does the Rio Grande Leave Colorado?

The Rio Grande flows southward out of the San Luis Valley and into New Mexico.

©CrackerClips Stock Media/Shutterstock.com

From its humble beginnings as a tiny stream, the Rio Grande grows rapidly as it flows south through the mountains. After passing through the San Juan Mountains eastward, it enters the San Luis Valley.

The San Luis Valley is the northernmost basin of the Rio Grande rift, a geological formation where the Earth’s crust has pulled apart. This tectonic rift began spreading apart over 30 million years ago, and it still today continues to widen very slowly.

The Rio Grande flows southward out of the San Luis Valley and into New Mexico.

Where in New Mexico Does the Rio Grande Flow?

Near the border of Colorado and New Mexico, the Rio Grande runs through the Rio Grande Gorge. This gorge was carved over millions of years by the river’s powerful current and is now designated as the Rio Grande del Norte National Monument. In the 1970s, Apollo astronauts trained for their moon missions here on the rim of this gorge.

The Rio Grande river continues its journey south through the middle of New Mexico. It then flows through the Española Basin and Albuquerque Basin—two more basins of the Rio Grande rift. These areas include the cities of Santa Fe, Albuquerque, and Las Cruces.

Just south of Las Cruces, the Rio Grande leaves New Mexico to become the border between Texas and Mexico.

Why is the Rio Grande the Border Between the United States and Mexico?

In the early 1800s, the land we now call Texas belonged to Mexico until 1836 when Texas declared its independence. Mexico and Texas had very different ideas about where their shared border should be. Mexico said it was the Nueces River—farther north—while Texas claimed it was the Rio Grande.

In 1845, the United States annexed Texas as a state, adding to the disagreement over where the border should be. This dispute set the stage for the Mexican-American War in 1846. After two years of fighting, the United States won, and Mexico was forced to sign the Treaty of Guadalupe Hidalgo in 1848.

In this treaty, Mexico agreed to sell nearly half its territory to the US, and the border between the US and Mexico was officially set at the Rio Grande.

How is the Rio Grande Maintained Between the United States and Mexico?

The International Boundary and Water Commission is responsible for maintaining the Rio Grande River.

©iStock.com/Greg Meland

Setting the border at the Rio Grande made sense at the time since it was the widest and deepest river in the area and serves as a natural barrier between the two countries.

But the Rio Grande, like any river, is always changing. Over the years, the river has shifted its course, sometimes changing quite dramatically from how it was in the 1800s. Also, flooding, erosion, and drought can create confusion for landowners in the area.

To address this confusion around the Rio Grande, the International Boundary and Water Commission (IBWC) was created in 1889. This organization is responsible for maintaining the river as the official border, and they work to resolve any water-related disputes between the US and Mexico.

Where Does the Rio Grande End?

The Rio Grande ends its journey at the Gulf of Mexico, at Boca Chica Beach. On the United States side, this area is designated as the Boca Chica State Park and Boca Chica Wildlife Refuge, where beaches and dunes provide a great destination for birdwatching, fishing, and swimming.

In that same area, immediately north of the mouth of the Rio Grande, is SpaceX’s Starbase spaceport. So while Boca Chica Beach is typically accessible to visitors, there are times when the area is closed off due to SpaceX launches.

Is the Rio Grande Navigable by Boat?

The Rio Grande is not deep enough to accommodate large cargo ships or other ocean-going vessels. However, in most areas, you can canoe, kayak, or raft down the river. Because of the changing water levels, it’s best to check with local authorities or experienced guides before planning a trip. You may also need a permit, depending on the stretch of river you’re planning to canoe.

As you float down the Rio Grande, you’ll see the marvelous sights created by millions of years of erosion in the volcanic basalt rock that forms the river’s canyon walls, as well as the diverse plant and animal life that call this area home.

What Type of Habitat is the Rio Grande River Area?

Rio Grande Village Hot Springs

The Rio Grande flows through a diverse range of habitats.

©Fred LaBounty/Shutterstock.com

The great length of the Rio Grand traverses many different types of habitats. At its headwaters in the high elevations of Colorado, the Rio Grande flows through a mountainous forest region. Then, after passing through the agricultural grazing land of the San Luis Valley, it reaches the Rio Grande Gorge—a deep, impressive canyon.

Then through the arid desert cities of Albuquerque, Las Cruces, and El Paso, the Rio Grande irrigates the nearby farmlands.

By the time it reaches the Gulf of Mexico, the Rio Grande enters a more tropical wetland environment.

What Animals Live in and Along the Rio Grande?

The Rio Grande passes through a diverse set of ecosystems, including mountains, forests, agricultural lands, and arid lands, as well as warm and tropical areas. This variety of habitat is reflected in the wide range of plant and animal life that lives in and around the river. 

The mountainous terrain of Colorado’s upper Rio Grande provides a habitat for bighorn sheep, elk, lynx, cougars, mule deer, pronghorn, black bears, golden eagles, and more.

In the southern plains area, snakes, ocelots, jackrabbits, javelinas, horned lizards, Texas tortoises, and many other species call the Rio Grande home.

The river itself is home to a number of fish, including minnows, trout, carp, catfish, bullheads, sunfish, bass, and so much more.

And, of course, the Rio Grande is vitally important to the human population in the area. An estimated 12-13 million people live along the Rio Grande—in Mexico and the US—and rely on the river for drinking water, irrigation, transportation, and recreation. For any nature enthusiast, the Rio Grande is an amazing river that offers a wealth of opportunities for outdoor adventure, wildlife spectating, and educational exploration.

The photo featured at the top of this post is © CrackerClips Stock Media/Shutterstock.com

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