US State Dept Records retention Dec 2008
pg 5
5. Retention
a. How long is information retained?
The established retention period for electronic records in PRISM is presently 100 years in accordance with published record schedules of the Department of State and as approved by the National Archives and Records Administration.
http://www.state.gov/documents/organization/96122.pdf
beat me to it
they are also microfilmed and given to the National Archives..
Since 1978, the State Department has been microfilming passport applications. Even when they are on microfilm, original papers are kept for 20 years. The microfilm is kept for 100 years. In addition, the department keeps forever any record of a birth or death of an American overseas.