Yes, keyword prominence in the URL is a ranking factor, according to Google’s spokesperson, Matt Cutts.

Keyword prominence refers to how close are the keywords to the beginning of the URL. In an interview, Matt suggested that the first five words in the URL are given the full weight:

“If you have got a three, four or five words in your URL, that can be perfectly normal. As it gets a little longer, then it starts to look a little worse. Now, our algorithms typically will just weight those words less and just not give you as much credit.” source