"Silicon Alley" is New York's answer to Silicon Valley. Here's an infographic (yes really) that breaks it down.
Who Said It?
The first use of the term 'Silicon Alley" was amazingly all the way back in 1995 by a New York Staffing Recruiter, Jason Denmark, who was recruiting in the newly dubbed technical hub in downtown Manhattan. In an effort to attract candidates who at that time were focusing on positions in Silicon Valley, Denmark posted several job ads in public usenet groups with the 'Silicon Alley' label to refer to New York City.