  For a positive integer n and a subset S of [n-1], the descent polytope DP_S
is the set of points x_1, ..., x_n in the n-dimensional unit cube [0,1]^n such
that x_i >= x_{i+1} for i in S and x_i <= x_{i+1} otherwise. First, we express
the f-vector of DP_S as a sum over all subsets of [n-1]. Second, we use certain
factorizations of the associated word over a two-letter alphabet to describe
the f-vector. We show that the f-vector is maximized when the set S is the
alternating set {1,3,5, ...}. We derive a generating function for the
f-polynomial F_S(t) of DP_S, written as a formal power series in two
non-commuting variables with coefficients in Z[t]. We also obtain the
generating function for the Ehrhart polynomials of the descent polytopes.
