Several new estimates for the 2-adic valuations of Stirling numbers of the second kind are proved. These estimates, together with criteria for when they are sharp, lead to improvements in several known theorems and their proofs, as well as to new theorems. The estimates and criteria all depend on our previous analysis of powers of 2 in the denominators of coefficients of higher order Bernoulli polynomials. The corresponding estimates for Stirling numbers of the first kind are also proved.Some attention is given to asymptotic cases, which will be further explored in subsequent publications.Keywords: Stirling numbers of the second kind, 2-adic analysis, higher order Bernoulli numbers and polynomials, estimates and exact values, Newton polygons. MSC[2010] : 11B68, 11B73, 05A10, 11S05.