Material connected with a particular public event, such as a political campaign or a parade, is often thought of as historically significant. But so are more private materials such as letters and diaries and snapshots. Please don't dismiss the historical importance of what you've collected because it isn't specifically about an obvious event. Historians need to reconstruct the conditions of the period they study. There are a few cardinal rules for conserving materials.
Moisture can directly destroy paper and fabric, or cause it to mildew and deteriorate over time.
Moist conditions also encourage vermin that can contaminate or destroy materials. A basement is not a good place to store materials you want to last. Keep it out of direct sunlight. Direct sunlight is especially damaging to photographs, but it can also fade printed matter and handwriting, make paper deteriorate more quickly, fade the color from fabric, and so on. Keep it cool.