A fort is a strong building or group of buildings designed to protect people during attacks. Forts have thick walls, strategic locations, and defensive features like towers where guards can watch for enemies. Throughout history, soldiers used forts to control important locations like mountain passes, river crossings, or territorial borders.

Many American forts played crucial roles in the nation's expansion westward. Fort Sumter, where the Civil War began, protected Charleston Harbor in South Carolina. Fort Knox in Kentucky, famous today for storing gold, started as a military post. Some forts were simple wooden structures with high walls, while others were massive stone fortresses that took years to build.

Kids often build backyard forts from blankets, cardboard boxes, or couch cushions. These playful versions capture the same basic idea: creating a defended space that feels safe and secure. When you fort up somewhere, you're settling in and making yourself secure, like fortifying your position with snacks and books on a rainy afternoon.