Final answer:
The Europeans wrote letters and documented their experiences when migrating west for communication, documentation, and establishing claims and dominance.
Step-by-step explanation:
When the first Europeans arrived on the eastern coasts of North America and started migrating west, they had multiple reasons for writing letters and documenting their experiences. One reason was the desire to communicate with their home countries and provide updates on their progress, discoveries, and challenges. These letters and diaries served as a form of documentation and evidence of their explorations. Additionally, writing about their experiences allowed the Europeans to share their encounters with the indigenous people, landscapes, and resources they encountered, providing detailed accounts for future reference and potential exploitation or colonization. Lastly, documenting their travels helped the Europeans establish a sense of identity and connection to their homeland, as well as establish their claims and dominance over the new lands.