A more thorough explanation:

A national monument is a special place that has been declared by the President of the United States to be important because of its history or science. It includes both the object or structure and the land around it.

For example, the Statue of Liberty in New York City is a national monument. It was given to the United States by France in 1886 and is a symbol of freedom and democracy. Another example is the Grand Canyon in Arizona, which is a national monument because of its unique geological features and natural beauty.

These examples illustrate how national monuments can be different types of places, but they are all important to the history or science of the United States. They are protected by the government so that people can visit and learn from them for generations to come.