Why didn't more African Americans move out West after the Civil War, and especially after Reconstruction? I know that the Hollywood image of all white cowboys is nonsense, and there were many black cowboys, as well as people in other types of work. Why didn't more African Americans settle there though, as in get married, raise a family, and so forth. At least to judge from many of those states current populations, that didn't happen much. Why? As I understand it, most of the people who moved West in that era were people who had few prospects in the East, which would certainly apply to many African Americans. I'm sure there was prejudice out West, but it seems hard to believe that it was worse than in the South.
I'm having trouble finding links to any academic texts, but quite a few Western states and communities actively worked to keep African Americans from settling in them. One of the more infamous examples is the set of exclusion laws passed in Oregon beginning in the 1840s. These laws, while banning slavery in Oregon, also banned black people from settling in Oregon.
This may not be considered a proper historical source, but it has the basic background of the Oregon situation.
There are many reasons. Many African Americans didn't move west because of employment and work. Even today the majority of African Americans still live in the South, about 55%. Only around 8% of African Americans reside in the West today. In 1910 90% of African Americans resided in the South. The only significant populations of African Americans outside of the South were in the North mostly in urban areas. The North was very economically and industrially developed and populated.
One of the reasons they remained in the South is Sharecropping. This system of farming had already existed in the South which used both poor white farmers and freed blacks prior to the Civil War. Afterwards, when the freed slaves were allowed to own property and land, many entered this system. This system isn't slavery but it certainly was no real improvement and bears resemblance to feudal agriculture even. Blacks to support their families entered into the system where they would practice subsistence agriculture and part of the harvest would be given to the landowner. While landowners would provide things to the sharecroppers, they would sometimes charge exorbitant prices. Often the working conditions were poor as well. Many blacks remained poor and stuck in this systems for many years.
Assuming they are not stuck in sharecropping leaving the South was difficult after the war as the U.S. government with military backing was restrictive on the South, black and white, to prevent insurrection and rebellion. The Southern States took time to be readmitted to the union.
Assuming they can leave they would need the money to go west. Going west wasn't something anybody just did it was a major decision and families in the east risked everything going west. It still cost a good deal of money to go west. The financial burden would have also kept many African Americans from going west.
If they they had the money to move, why go west? What will they do there? As previously mentioned it was a big risk to go west as reliable employment was not to be found out west. Meanwhile the North was economically booming and they would have a far better chance of finding employment there. There were fewer population centers in the West and none as populous as in the North.
Even then, not as many went North. Many African Americans would not be able to afford the move out of the South and were stuck in sharecropping. While more employment could be found in the North thy would have had competition. Millions of immigrants from Europe were arriving such as the Germans(around 20% of Americans have German ancestry), Irish(15%), and Italians(5%). I skipped many other European ethnicities that also came over.
By 1900 there were few significant communities of African Americans outside of the South. Far fewer after taking out the North. So while as you said cowboys of other races probably and most likely did exist, based on demographics I would predict there would be few though. In the West the larger minority would probably be Asians of various descents though mostly Chinese. Though later exclusion acts slowed immigration. Hispanics is a tricky thing to discuss as they weren't counted in the census until the past few ones. Hispanics are also not a race. They are part of culture influenced by Spain and Spanish colonization. They could be of any race. That being said the majority of Hispanics in the U.S. identify as white. After that would be people of mixed descent though mainly mixed European and native descent.
African American migration out of the South was best seen in what was known as the Great Migration during the mid 20th century where many moved to urban centers around the U.S.
Hope to have helped. If you need more info I'll see what I can find.