Kinmen has the third highest of gazetted historical sites among the cities and counties of Taiwan, after Taipei and Tainan, both of which are present and past capitals of Taiwan. For an island with less than 200 sq km, Kinmen has the highest density of historical sites in Taiwan. One reason for this was the historical importance of the island as a naval base of coastal China. The other was that because the island was for a long time a sensitive frontier zone with restricted access to outsiders for many decades during the ROC/PRC conflict, it had not been subjected to the relentless tear-and-destroy economic development that the rest of Taiwan (or ROC) had seen.
If ever Taiwan could get its sites listed as world heritage, I suspect Kinmen's sites would probably qualify.