National Trails System Improvements Act of 1988

National Trails System Improvements Act of 1988 - Amends the National Trails System Act to retain to the United States interests in abandoned railroad rights-of-way. Requires such retained rights-of-way located within the boundaries of a conservation system unit or a national forest to be incorporated within such unit or forest and managed appropriately. Requires such rights-of-way outside such boundaries but adjacent or contiguous to public lands to be managed pursuant to the Federal Land Policy and Management Act of 1976. Requires the Secretary of the Interior to manage other suitable rights-of-way for use as public recreational trails or other recreational purposes, provided such uses do not preclude trail use.

Authorizes the Secretary to release and quitclaim to a unit of government or other qualified entity for public recreation use, upon application, such rights-of-way located outside the boundaries of a conservation system unit or national forest. Requires such unit or entity to assume full responsibility and to hold the United States harmless for any liability arising out of such release or quitclaim. Permits the Secretary to sell portions of such rights-of-way which are also not adjacent or contiguous to public lands. Requires any proceeds to be deposited in the Treasury, credited to the Land and Water Conservation Fund, and reported to the Congress.

Extends the life of the Iditarod Historic Trail Advisory Council to 20 (currently ten) years from the date of its establishment.

Declares that nothing in this Act should be construed to authorize the Secretary to use condemnation to retain or acquire all or any portion of a right-of-way described in this Act, or to expand or diminish existing condemnation authority contained in the National Trails System Act, as amended.