I think the Muratorian fragment is essential to establishing a canonicity discussion that shows an early third century, informal recognition of the NT canon.
Though some, mostly more conservative evangelicals, try to push for a very dating on the fragment, I can't realistically place it before AD 200. Other supporting documentation affirms the fragment and, the result of the canonicity process also helps. It seems pretty evident that early texts were circulating, though it isn't clear that any formal attempt at canonicity was seen to be necessary prior to the rise of some heretics in the second century and beyond.
What is so interesting about this discussion, and particularly for most theological formation in the period, is that the canon wasn't seen to be entirely necessary until the rise of false teachers and heretics. At that point the orthodox Christians of the early Church began pulling together legitimate books to contravene the proposals of the heretics.
Most particularly the influence of Marcion with his limited canon pushed this issue more than nearly anyone else. The Montanist controversy also was important.
As a result, the early Church began formally pushing towards a formal canon, but not until prompted by necessity.
Some will disagree, but I think the evidence is pretty substantial for such an observation.