The Gilbert-Maxam method for sequencing DNA. This paper is available from PNAS at this link.

In 1980 Gilbert shared the 1980 Nobel Prize in Chemistry with Frederick Sanger and Paul Berg. Berg received half of the prize "for his fundamental studies of the biochemistry of nucleic acids, with particular regard to recombinant-DNA". The other half was split between Gilbert and Frederick Sanger "for their contributions concerning the determination of base sequences in nucleic acids."