The first question that a frightened world asked about Three Mile Island on 28 March 1979 was how long the place could be expected to stay on the map. As fear subsided enough to suggest that it might be there for a long time, the question shifted to the more curious, "How did the place get its unusual name?" That question is not simply answered; six years of curiosity and research have yielded more conjectures than proofs.
It is known that on 4 December 1749 Thomas Cookson, surveyor who in 1751-1752 laid out and purchased the town site for Carlisle, asked Thomas Penn for permission to buy the future Three Mile Island. When he died in 1753 Cookson had not completed his acquisition, but the land appeared in his estate records merely as an unpurchased, unnamed "island in the Susquehanna."