Complex sentence: A delegation from the Cherokee Nation West, including Sequoyah, travels to Washington City where they are pressured into signing the Treaty of Washington giving up their lands in Arkansas Territory for lands in Indian Territory that are essentially what becomes the Cherokee Nation after the Removal.
Split into simpler sentences: A delegation from the Cherokee Nation West, including Sequoyah, travels to Washington City where they are pressured into signing the Treaty of Washington. They cede their lands in Arkansas Territory for lands in Indian Territory, which essentially are the basis for the Cherokee Nation after the Removal.