Dictionary.net

The first pre-emption act was passed March 3, 1801. It was a special act affecting the Symmes colonization scheme on the Miami River. Between that time and 1841 about eighteen pre-emption acts were passed, all of a more or less special nature. The first general law was passed in 1830. That of 1841, which is now in force, grants, upon considerations of residence and improvement, freedom of entry upon 160 acres of public lands to any person over twenty-one years of age. Twelve to thirty three months are allowed for payment, and the amount varies with the value and situation of the tract pre-empted.