Samuel Snyder began his career as an "assistant cryptographic clerk" with the U.S. Army's Signal Intelligence Service in 1936. He was one of the first ten employees in that organization, which was a predecessor to NSA. During World War II, he led large teams that exploited Japanese army cryptosystems.

Noticing that use of sorting machines for cryptanalytic support was haphazard, Snyder suggested a more systematic approach to William Friedman, and Friedman tasked him with developing it. Snyder's innovations made special-purpose devices a strong asset in rapid wartime exploitation of enemy communications.

After the war, Snyder carefully researched what was known about the new field of computing and in 1952 was instrumental in designing and building ABNER, a then-sophisticated computer that took advantage of advanced technology.

During the 1950s, Snyder conducted in-house research and worked with outside contractors to design and build three more powerful systems. The last of these was HARVEST, one of the first general-purpose computers. HARVEST greatly expanded NSA's computing capabilities, but also had significant influence on the commercial computer market.

In 1964 Snyder became an information systems specialist for the Library of Congress and was one of the creators of the library's Machine Readable Cataloging (MARC) system for bibliographic data. This became an international standard for data sharing in research.

Samuel Snyder's pioneering work in early computers led directly to the development of the computer as we know it, and laid the foundation for many aspects of the modern computing industry.