Read the following excerpt from a historical article:
'The construction of the transcontinental railroad was a monumental undertaking, driven by economic ambition and nationalistic pride.
While it undeniably spurred westward expansion and integrated the national economy, it came at a significant cost.
The displacement of Native American tribes, the harsh labor conditions for immigrant workers, and the profound alteration of the natural landscape are critical aspects of its complex legacy.'
Which of the following statements best analyzes the author's purpose in this excerpt?