Various digitized Civil War letters from various states -- plus a few portraits and diary excerpts can be found here:
http://content.lib.washington.edu/cdm4/browse.php?CISOROOT=/...I think these are all the authors:
Alexander Parker Crittenden to his wife Clara Crittenden
Arthur Tappan Strong diary
Arthur Tappan Strong from his friend Robert
Capt. James A. Sayles to his sweetheart Florence Lee
Captain Charles M. Scott to his wife Anna
Captain Isaac N. Chenoweth to his friend Jasper N. Bertram
Captain L. Silbert to Brigadier General L.A. Grant
Captain Watson Squire to his mother and to his parents
Captain William McMicken to his daughter Nellie
Captain William McMicken to his wife Rowena Ostrander McMicken
Churchill Jones Crittenden to his mother Clara Jones Crittenden
Churchill Jones Crittenden to his uncle George W. Jones
Churchill Jones Crittenden to his parents Alexander and Clara Crittenden
Coast Survey Office condolence to Margaret Hazard Stevens regarding Isaac Stevens' death
David H. Bertram to his parents
Ellen to her cousin Jasper N. Bertram
Florence Lee to her sweetheart Captain James A. Sayles
Florence Lee's transcription of a letter from General L.A. Grant to his sister Mrs. E.G. Sayles
Georgia Sayles to her cousin Captain James A. Sayles
Hazard Stevens to his mother Margaret Hazard Stevens
Henry B. Tolle to his friend Jasper N. Bertram
Henry Sheak to Jasper N. Bertram
J.H. Barbour to his friend Jasper N. Bertram
James Bertram to his cousin Jasper N. Bertram
James Crittenden to his mother Clara Jones Crittenden
James Crittenden to his parents Alexander Parker and Clara Jones Crittenden
James S. Dupray to his sister Ruth Dupray Morgan
Jasper N. Bertram's 1864 Civil War diary
L.A. Grant to his sister E. G. Sayles
Lieutenant Colonel E.M. Pope's to Florence Lee
Lucinda J. Tolle to her friend Jasper N. Bertram
Lucinda J. Tolle to Jasper N. Bertram
Lyman W. Strong to his son Arthur Tappan Strong
Lyman Whitney Strong Jr. to his brother Arthur Tappan Strong
Lyman Whitney Strong to his son Arthur Tappan Strong
Mary A. Chenoweth to her friend Jasper N. Bertram
Mary Custis Lee to Union General Sanford
Philip Van Buskirk diary
Rebecca Jones Craigel to her sister Clara Jones Crittenden
Riley M. Hoskinson to his wife Martha Hoskinson of Rushville
Rowena Ostrander McMicken to her husband Captain William McMicken
Ruth Maria Strong to her son Arthur Tappan Strong
S.D. Dunmire to his friend Ruth Dupray Morgan
Samuel D. Lougheed to his wife Jane "Jennie" Lougheed
Sarah E. Denham to Jasper N. Bertram
William Dupray to his sister Ruth Dupray Morgan & brother-in-law H. Morgan
William H. Smith to his friends
William T. Patterson diary excerpt