Another fun fact. You don't see box sets of all the movies because Romero always had to raise money from different people so the rights for them (other than the first) are scattered.
Not only that, but Duane Jones got the role solely on merit. The part was not written with an African-American (or a minority) in mind, but Romero decided after the fact not to update the script in any way, which gives the film this odd colour-blind/progressive trait for that time (1968)...
(Mild spoiler below)
...And then post-filming but before its release, Dr Martin Luther King Jr was shot, giving the film's treatment of Jones character an unexpected tone in context. Romero mentioned this in one of his interviews to illustrate another way in which the film was shocking to its audience (beside the then never-seen-before level of gore in the movie -- something that has gone mainstream since then and may get lost when watching the movie).
As Jordan Peele said about his Get Out, "This is the only woke horror movie of all time, save for Night of the Living Dead. ... I felt like race has not been dealt with in my favorite genre which is horror. Every other human horror has its sort of classic horror movie to go along with it. So I kind of wanted to fill the gap in that piece of the genre of conversation." (http://www.npr.org/2017/02/19/515813914/in-get-out-jordan-pe...)
There is a weirdly slow car crash scene in Night Of The Living Dead - this was written into the script since someone borrowed the car and drove a dent into it, and they needed to explain the new dent in the movie...
One of the things about the film was how the humans treated each other far worse than what the zombies did to them. The zombies (the slow kind!) were just a force of nature.
