The cusped hyperbolic n-orbifolds of minimal volume are well known for $n \leq 9$. Their fundamental groups are related to the Coxeter n-simplex groups $Γ_n$ listed in Table 1. In this work, we prove that $Γ_n$ has minimal growth rate among all non-cocompact Coxeter groups of finite covolume in $\hbox{Isom}\mathbb H^n$. In this way, we extend previous results of Floyd for $n = 2$ and of Kellerhals for $n = 3$ respectively. Our proof is a generalisation of the methods developed in [2] for the cocompact case.