Physiographic Regions of the Western United States (map generated by web site).

Physiography is another term for Physical Geography, or Geomorphology; a subfield of Geography dedicated to studying natural features and the physical patterns and processes of the Earth. Physiography attempts to understand and organize the forces shaping rocks, rivers, plants and animals. A geographic area’s climate, underlying geology and geological history all affect what you see atop the land today. Physiography is essentially a way of understanding what you’re looking at.

A bit of snooping around on the web led me to a ‘forgotten’ book by Nevin Fenneman, a geology professor at University of Cincinnati in 1930. Professor Fenneman literally wrote the book on Physiography. Though nearly 100 years old, the miracle of modern technology saw a copy of it land on my desk this week. I am enthralled, which I acknowledge as a little weird.

“The central theme of the work is the land forms of Western United States and how they came about. There is no doubt about this center of interest, but the circumference of an appropriate mass of fact may be hard to fix. It may be assumed that geologists and geographers have equal interest in land forms, but the quality of their interests is very different. To the geologist land forms are a kind of final product, the end of a story. To the geographer they offer a beginning, a point of departure. To the former, land forms depend on all physical processes of geology. To the latter, they depend on nothing; almost everything else depends on them in some measure.”

(from the Preface of “Physiography of Western United States,” by Nevin Fenneman, Professor of Geology, University of Cincinnati, 1930)


A little light reading to unwind, Allenspark, Colorado

I stumbled upon Physiography while researching questions surrounding the difference between different geographic regions. For example, what’s the difference between the Basin and Range Province and the Great Basin? Or what distinguishes The Rocky Mountains System from the Northern, Middle or Southern Rocky Mountains? Or what is the relationship between the Great Plains and the Colorado Piedmont? In asking these questions I discovered a deep desire to understand how these various regions connect, overlap or exist relative to one another.

Iowa River wetlands along Route 20, Central Iowa.


Iowa River wetlands along Route 20, located in the Central Lowlands Province.

One of the first things I want to know when viewing a photograph is ‘where.’ For me, physiography has become a good start in the attempt to categorize a large amount of visual data (photographs) amassed over years of traveling and photographing. The goal is to organize these photographs into a coherent structure. There’s a easy to understand map on the National Park Service website located here, used to create the above graphic’s base.

Descending from Snowy Range towards the Little Snake River Valley


Snowy Range, Saratoga, Wyoming

Physiography categorizes the Earth’s topographic features into various, distinct areas based the approach established by Nevin M. Fenneman around 1916. Fenneman’s 3-levels of classification approach places geographic features separating land forms into Regions (highest level), Provinces (second level) and Sections (third level and most numerous). Even though the areas are considered distinct from a geographic point of view – often from the ground, there’s no real way to distinguish one from another. The photograph above, for example, is what it looks like in central Wyoming as one transitions from the Central Rocky Mountain Province to the Wyoming Basin Province. That’s where the 10,000-foot view can come in handy, and what this section of Blue Hour Journal explores.

A) There are 8 top level Physiographic Regions in the United States:

  • Appalachian Highlands Region
  • Atlantic Plains Region
  • Interior Highlands Region
  • Interior Plains Region
  • Intermontane Plateaus Region
  • Laurentian Uplands Region
  • Pacific Mountain System Region
  • Rocky Mountain System Region

B) There are then 24 distinct Physiographic Provinces. Being a resident of the West, I’m primarily interested in the 7 Physiographic Provinces of the Western United States. In alphabetical order they are:

  • Basin and Range Province
  • Cascade-Sierra Mountains Province
  • Colorado Plateaus Province
  • Columbia Plateau
  • Great Plains Province
  • Pacific Border Province
  • Rocky Mountain Systems Province

C) These Provinces may then be further divided into Physiographic Sections. For example:


Tonopah, Nevada (1992). Much of Nevada is located in the Basin and Range Province.

1. The Basin and Range Province is sub divided into 5 sections:

  • Great Basin Section
  • Mexican Highland Section
  • Sacramento Section
  • Salton Trough Section
  • Sonoran Desert Section

Liberty Bell Peak and Washington Pass, Okanogan-Wenatchee National Forest, Washington (2017)


Liberty Bell Peak and Washington Pass, Located in the Northern Cascade Mountains. Okanogan-Wenatchee National Forest, Washington.

2. The Cascade-Sierra Mountains Province focuses on two main mountain ranges:

  • Northern Cascade Mountains
  • Middle Cascade Mountains
  • Southern Cascade Mountains
  • Sierra-Nevada


Mante LaSalle Mountains and Canyon Lands – both located in the Colorado Plateau Province, Utah

3. The Colorado Plateaus Province straddles the area known as Four Corners and covers large portions of Arizona, Utah, New Mexico and Colorado. Some of the best known and most visited National Parks are located in the Colorado Plateaus Province, such as Arches, Grand Canyon, Capitol Reef, Cedar Breaks, Colorado National Monument, Dinosaur National Monument, Mesa Verde, Petrified Forest, Chaco Canyon, Canyon de Chelly and Zion National Park, to name just a few.

  • High Plateaus of Utah
  • Uinta Basin
  • Canyon Lands
  • Navajo Section
  • Grand Canyon Section
  • Datil Section


Columbia Plateau, Oregon

4. The Columbia Plateau is Dominated by one of the world’s largest accumulations of lava, and divided into 5 sections:

  • Walla Walla Plateau
  • Blue Mountain Section
  • Payette Section
  • Snake River Plain
  • Harney Section

American Bison near Grover, Colorado


American Bison near Grover, Colorado. The western edge of the Great Plains Province butts up against the Rocky Mountain Province.

5. The Great Plains Province has emerged as a strangely fascinating region to me. In the context of Blue Hour Journal, the Great Plains occupy the eastern portion of my home state of Colorado, as well as bordering neighboring states of Wyoming, Nebraska, South Dakota and Kansas, which I travel regularly. The Western edge of the Great Plains definitively come to a halt where they meet the Rocky Mountains. To the East, the Great Plains Province trails off gradually into the Central Lowlands Province, which we won’t focus on here because even though there’s really no official marker, the Central Lowlands are definitely not considered the Western US. Perhaps one reason the Great Plains arouse my interest is their relatively overlooked and unassuming role as compared to their more dramatic and heavily traveled neighbors. This fits well with my admiration and respect for the understated.

  • Missouri Plateau (Glaciated)
  • Missouri Plateau (Unglaciated)
  • Black Hills
  • High Plains
  • Plains Border
  • Colorado Piedmont
  • Raton
  • Pecos Valley
  • Edwards Plateau
  • Central Texas

Blue Hour, Rialto Beach, Olympic National Park, Washington


Blue Hour, Rialto Beach, Olympic National Park, Washington

6. The Pacific Border Province forms the western edge of the continent located between the Pacific Ocean and the western edges of mountain ranges like the Sierra Nevada and Cascades. Encompassing Washington, Oregon, California and northern Mexico, it’s divided into 7 distinct topologies or Sections:

  • Puget Trough
  • Olympic Mountains
  • Oregon Coast Range
  • Klamath Mountains
  • California Trough
  • California Coast Ranges
  • Los Angeles Ranges (Transverse Ranges)


Delaney Butte, North Park, Colorado. Sometimes names get confusing. North Park lives in the Southern Rocky Mountain Section.

7. The Rocky Mountain System Province is my home turf. It stretches from Canada to Mexico and is further divided into the following 4 sections:

  • Northern Rocky Mountains (Canada and Montana)
  • Middle Rocky Mountains (Wyoming)
  • Wyoming Basin (northwest Colorado and Wyoming)
  • Southern Rocky Mountains (primarily Colorado, parts of southern Wyoming and northern New Mexico)

The idea is, each of these Physiographic Regions, Provinces and Sections helps identify each region (using that term generally speaking now) and forms a better picture of an area and how it relates to those around it.

North Park, Colorado


My Happy Place, North Park, Colorado.

Over the next several months I’ll build out each category, providing photographs along the way. My hope is that Physiography becomes a way to help answer the question a little more coherently of ‘where’ while at the same time providing a little information along the way regarding the how or why of an area.

But this isn’t a lesson in Geography, I promise. Truth is, I’m learning as I go and don’t pretend to be an expert.

But I am passionate about the topic and eager to get it right. So if there’s anything errant on any of these pages – please – let me know.