In 2001, an appeals court ruled that New Jersey's practice of not allowing anyone to register to vote as anything other than Democrat, Republican, or Independent was unconstitutional. This was the result of a lawsuit brought by a coalition of political parties, including the NJ Libertarian Party.
Since then the number of registered libertarians has been steadily growing. The 2016 numbers show 5,391 registered Libertarians. This is a 109.5% growth from the prior year.
We are 77% larger than the next biggest party (the Green Party at 3,049) making us without a doubt the largest third party in the state of New Jersey.
Summary of Registered Libertarians
Note that for most numbers it is as of the general election.