One idea is to give each student a nonfiction book that focuses on little-known facts and events about colonial America, and ask them to write a five-page informative essay on the book. In the essays, the students should start with an interesting introduction and they should also include some outside research on the little-known facts in addition to what's in the book. When the students return to class, you can have each student prepare a mock fifteen-minute feature news segment in which they discuss their essays.
Another idea is to divide your students in groups of three and assign them a key event during the 20th century about which they will write and perform a skit. One group may perform a skit about America's role in World War II while another group may perform a skit about the Great Depression of the 1930s. You should first talk with the students about how to write dialogue for the skits and give them a week to prepare them. After the students perform their skits, you can give feedback.
If you're interested in teaching the diverse contributions of minorities to American culture, you can have each student write a three-page report on an ethnic group that has done great things for the country in areas such as economics, politics, law and entertainment. Each student can choose her own ethnic group. The report should include some background information on how the group came to America as well as notable people from the ethnic group and their accomplishments.
Another idea is to have each student write a ten-page research paper about the roles of women throughout American history, and to write about a certain aspect of this issue. One student can write about how American society viewed single women throughout its history while another student may write about the struggles of immigrant women in America during the 19th and early 20th century.