He worked on the first California Geological Survey and was the first Chair of Agriculture at Yale University's Sheffield Scientific School.

In 1848 Brewer attended Yale and began studying soil chemistry under Professors Benjamin Silliman and John Pitkin Norton.

In 1855 Brewer travelled to Europe where he studied natural science under Professor Robert Bunsen at the University of Heidelberg in Germany.

[3] Brewer led field parties in the extensive survey of the geology of California until 1864, when he became the Chair of Agriculture at Sheffield Scientific School.

Brewer wrote extensively during the survey including many letters to family and friends, a compendium of which was eventually published by the Yale University Press in 1930 as Up and Down California in 1860-1864.