NEW ORLEANS — A marathon project is underway in New Orleans to digitize thousands of time-worn 18th-century French and Spanish legal papers that historians say give the first historical accounts of slaves and free blacks in North America.

Yellowed page by yellowed page, archivists are scanning the 220,000 manuscript pages from the French Superior Council and Spanish Judiciary between 1714 and 1803 in an effort to digitize, preserve, translate, and index Louisiana’s colonial past and in the process help revise American history.