Hummelstown Brownstone is a type of rock that is found in a town called Hummelstown, which is in Pennsylvania. The rock is a type of sandstone that is a brownish-red color.
Think of it like playing with sand at the beach. Hummelstown Brownstone is like a really special type of sand that is only found in one place.
People have been using Hummelstown Brownstone for a really long time to make buildings and other things. Because the rock is so strong and durable, it's great for making things that need to last a long time, like buildings and bridges.
So, Hummelstown Brownstone is kind of like a special type of rock that people use to build really cool and important things that they want to last a long time.