Using Finder, you can press Cmd-Shift-G and type /usr to display this folder. The /local folder is by default, but not in the /src subfolder. Finder, of course, can easily create one for you.

As mentioned in @ cricket_007, you need to be sure what you are doing in this area of ββthe system - why OS X does not show these folders by default. If you understand the risk and want to see everything in Finder, you can issue the following terminal command:
defaults write com.apple.finder AppleShowAllFiles YES
... then enter:
killall Finder
and it will look like this. Hidden folders have a slightly faded appearance, but you can navigate to them as desired: 
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