Not an article, but Kirk McKusick (a very longtime developer of BSD) gave a few talks on BSD and UNIX history (and the beginnings of TCP/IP), which are on YouTube: https://www.youtube.com/watch?v=bVSXXeiFLgk
If you prefer text, you can find it in Chapter 1 of his book "The Design and Implementation of the FreeBSD Operating System": https://www.amazon.com/Design-Implementation-FreeBSD-Operati... (the chapter seems to be available in the book preview)
Eric S. Raymond also wrote a nice chapter on UNIX history in "The Art of Unix Programming": http://www.catb.org/esr/writings/taoup/html/historychapter.h...