More Suggestions for the Portfolio Book
You might want to look at these books:
The Dear America Series, including titles about the Salem Witch Trials, the Gold Rush, the Titanic, the Suffragettes, the Mayflower, and many more, including The Great Railroad Race: the Diary of Libby West, Utah Territory 1868.
The My Name is America series, including titles about the marine corp in Vietnam, the Cherokee and the Trail of Tears, World War II and Normandy, the Civil War, the Lewis and Clark Expedition, the internment of Japanese Americans during World War II, pilgrims, an Alaskan whaling ship, the Donner Party.
The Royal Diaries, including titles about Catherine the Great, and royalty in Japan, Sweden, Egypt, Hawaii, and more.
If you look for the Dear American series, be careful because there is series with a similar title that is written for much younger children. Those wouldn't be appropriate for most seventh graders.