Much of the work of early black scientists and inventors is largely unknown, because of the fact that historians failed to record such accomplishments and slaves were for bidden from receiving patents. Instead, patents were assigned to their masters, for slaves were not considered citizens and were forbidden from entering into contracts with their owners or the government. Efforts of slaves were largely dismissed or, if accepted, credited entirely to their masters. It was not until 1790 that the federal government passed the U.S. Patent Act. This legislation gave inventors, including free blacks, the right to patent their inventions. For slaves, however, that right was delayed until the Fourteenth Amendment was passed. Some accounts of slaves as inventors emerged, as, for example, in the case of the McCormick harvester. It is said that Joe Anderson, a slave of grain harvester Cyrus McCormick, played a major role in the creation of the harvester, yet the degree of his involvement is undetermined. Benjamin Montgomery, one of President Jefferson Davis’s slaves, is thought to have invented an improved boat propeller.