Wikipedia (read the first paragraph to find out which states are included in this region) There's a lot of good information here, but you need to read the section heading to decide which parts you need to read more. There are good sections on climate, economy, and landforms (they call that "Geography").
What is the Northwest? This one also identifies which states can be included in this region. (Hint: There are really two major US states included, but a couple others sometimes get included as well.) Since we are just studying the US, don't worry about the Canadian province that is also part of this region.
World Book Kids (This site gives information about each state. If you read about the different states in this region, you can start to put together the puzzle of what the region is like.)
Scroll down to find Britannica School Elementary Near the bottom tap "Tour the USA." (Double click on a state to get more info. about it. Then tap "summary" and "read article" to get some more tabs with more great information.) Easy to read! If you need even more information, change the reading level to 2 to get more (tap on the purple square with a 2 in it near the top-center of the screen).
Scroll down to find Kid InfoBits Tap on Geography. Tap on U.S. States. (Use this site to research individual states.)
The North Pacific Coast This one uses advanced language, but if you sort through it, you can find information on the landforms and climate (in the section called The Physical Environment), population factors (in the section called Patterns of Human Occupation), and economic industries (in the section called The Regional Economy).