Susan Wojcicki, who helped turn Google from a start-up in her garage into an Internet juggernaut, and who became one of Silicon Valley’s  most prominent female executives with her leadership of YouTube, died on August 9. She was 56.

Ms. Wojcicki’s more than two decades with Google began in 1998 in her house in Menlo Park, CA, part of which she rented to her friends Larry Page and Sergey Brin, the company’s founders. For $1,700 a month, the two used the garage as their office to build the search engine.

Ms. Wojcicki, who had been working at Intel, soon joined Google as one of its earliest employees, and was its first marketing manager. Over the years, she reached its executive ranks, becoming Google’s most senior woman employee, eventually leading YouTube, which Google acquired in 2006, and which became one of the world’s largest social media companies.