What events of the 1830s is shown by the heavy black lines on the map?

The heavy black lines on the map likely represent significant territorial changes or boundaries established in the 1830s, such as the forced removal of Native American tribes through policies like the Indian Removal Act of 1830. This led to events like the Trail of Tears, where thousands of Native Americans were relocated from their ancestral lands in the Southeastern United States to designated territories west of the Mississippi River. Such actions were part of broader themes of westward expansion and the government's attempts to assert control over new territories during that decade.