African Americans in Baltimore
Freedom Records (also called Manumissions) for Baltimore City are available in electronic form online at Baltimore City Freedom Records.
The Maryland State Archives has put together an excellent overview of African Americans in Baltimore at From Frederick Douglass to Thurgood Marshall: Black Baltimore in Transition. Also helpful is their more overarching page on The Study of the Legacy of Slavery in Maryland, which has many useful links.
Also take a look at the section of the bibliography based on the work of Dean Krimmel, Anita Kassof, and Richard Longstreth entitled The African-American Experience in Baltimore and Maryland.