Final answer:
The U.S. government justified destroying the buffalo populations in the Great Plains to build the transcontinental railroad due to their belief in Manifest Destiny and economic benefits of westward expansion. However, this decision had devastating consequences for Native American tribes.
Step-by-step explanation:
The U.S. government justified destroying the buffalo populations in the Great Plains to build the transcontinental railroad due to their belief in Manifest Destiny and the economic benefits of westward expansion. The destruction of the buffalo herds was seen as necessary to clear land for agriculture and create a national market economy. However, this decision had devastating consequences for Native American tribes whose economies were dependent on the bison.