Illinois Civil War Muster and Descriptive Rolls Database (Illinois State Archives):
     Thayer, Caleb H - Pvt - Co A - 9 IL US CAV
      Residence, Chicago, Cook Co, IL; Join, 11Oct1864; Age, 31; Born, OH
      Height, 5' 5"; Hair, light; Eyes, blue; Complexion, light; Carpenter
      Mustered out, 26Oct1865
American Civil War Soldiers (ancestry.com)
      
Civil War Soldiers & Sailors System Search Detail (National Park Service):
        
National Graves Registration Database (Sons of Union Veterans of the Civil War):
     Thayer, Caleb H - 9 Illinois Cavalry
     Died, 25 Aug1921; Buried, Oakwood Cemetery [Joliet] Will county, Illinois
Honor Roll of State of Illinois, Illinois Veteran's commission, Oct. 1, 1956:
     Thayer, Caleb H. - Pvt - Co H - 9 IL Cav
      Died, 23Aug1921; Buried, Oakwood Cemetery, Joliet, IL, Section 23      
Will County Illinois USGenWeb Necrologist Reports (© 2002 The ILGenWeb Project All Rights Reserved):

Headstone Reading,

Published Obituaries:  

Joliet Herald News, Wednesday, August 24, 1921

    Caleb H. Thayer, former Joliet contractor and Civil War veteran, died yesterday afternoon at 5 o'clock at his home, 209 Campbell street. Mr.Thayer would have been 88 years old; Sept. 12. Altho he has been under a physician's care, his condition was not considered serious. He was up yesterday, his condition not seeming critical. He grew weaker during the day and died at 5 o'clock.
    He was an officer in Bartleson Post G.A.R. at the time of his death and was a past commander. Born in Cincinnati, Ohio, he came to Joliet, 48 years ago. Several years ago he retired from the contracting business. During the Civil War he served in the Ninth Illinois Cavalry. He was always an active figure in G.A.R. activities and took part in the Memorial day parades with his comrades of the Civil war.
    Surviving him are his widow, three daughters, Mrs. Ida Whittington, Mrs. Nettie Weishaar and Mrs. Grace E. Garretson and a son, Joseph Thayer. Funeral services which will be private, will be at the home Thursday afternoon at 3 o'clock. Burial will be in the family lot at Oakwood cemetery.

Additional Biographical Material:
    Born:  12 September 1833, Highland County, Ohio
    Died:   23 August 1921, Joliet, Will County, Illinois
    Parents:  Joseph Thayer, Eliza Windamaker  
    Married:   Joanna Murphy