Here is the next section of the first part of Strunk and White's Elements of Style: ELEMENTARY RULES OF USAGE.
"2. In a series of three or more terms with a single conjunction, use a comma after each term except the last.
red, white and blue
gold, silver or copper
He opened the letter, read it, and made a note of its content.
This comma is often referred to as the "serial" comma.
In the names of business firms the last comma is usually omitted. Follow the usage of the individual firm.
Little, Brown and Company
Donaldson, Lufkin & Jenrette