I am lookinbg for any information on Admiral George E.Belknap,
Commanding Asiatic station, Yokohama, until Febuary 1892 when he
retired. How do access any letters,or documents he may hacwe recieved
or written while he was commanding officer in Japan.

According to the WorldCat library catalog the Library of Congress
among many other libraries have copies of his manuscripts:

"George Eugene Belknap, Reginald Rowan Belknap: a register of their
papers in the Library of Congress."

The Naval War College in Rhode Island has the following materials:

              "Oral history typescript reminiscences of her family,
including
              grandfather George Belknap and her father ADM Reginald
              R. Belknap, CO, Yankee Mining Squadron." 
              Author: Howard, Mary R. Publication: 1930-1985 

             "Papers of Rear Admiral George E. Belknap and Rear
Admiral Reginald R. Belknap,
          1830-1957" 
          
          Correspondence of George E. Belknap, chiefly letters to his
wife, Frances Georgiana
          Prescott Belknap, concerning career and family matters, and
miscellany; incoming and
          outgoing personal correspondence of Frances Belknap,
including letters focusing on family
          matters and navy life in Japan when Belknap served as
commander in chief, Asiatic Station
          Naval Force; incoming and outgoing correspondence of
Belknap's son, Reginald R....

Sorry abount the spacing in the post.  Contained in the quotes is the
title of the material.  What follows is a short decription.