SOURCE OF TITLE  in many states refers to a document defined under state Marketable Title Acts that have been enacted in almost half of the 50 states, Some  statutes are titled "Marketable Record Title Act (MARTA)" The Acts statutorily remove title defects of ancient origin, and act as a statute of limitation to clear the public record of old property rights that cloud title. 

Many interests of ancient origin, are liable to extinguishment unless appropriate measures are taken by their holders or claimants to place a claim of their  interests on the recent records. The Acts also establish procedures for recording notice of any interest prior to the period prescribed for the record search. They tend to  vary by state in:<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

• The property interests that are extinguished under the Act
• The periods of limitation (up to 60 years)
• The periods of time required for recording notices of a claim
• The exceptions contained in the acts (for government rights, churches, etc.) 

I believe the following states have marketable title acts Colorado, Connecticut, Florida, Kansas, Illinois, Indiana, Iowa, Michigan, Minnesota, Nebraska, North Carolina, North Dakota, Ohio, Oklahoma, South Dakota, Utah, Vermont, and Wyoming. (There may be others as well)