Who was Richard Nixon's first vice president?

In 1952, when Nixon was elected Vice President, Alben W. Barkley of the Democratic Party was the Vice President.
In 1956, when Nixon was re-elected Vice president, Nixon was of course the Vice President.
In 1968, when Nixon was elected to the presidency, Hubert Humphrey was the Vice President, whom Nixon also defeated in the election.
In 1972, when Nixon was re-elected, Spiro Agnew was the Vice President.