We study antiferromagnetic spin--1/2 Heisenberg ladders, comprised of $n_c$ chains ($2 leq n_c leq 6$) with ratio $J_{bot}/J_{|}$ of inter-- to intra--chain couplings. From measurements of the correlation function we deduce the correlation length $xi(T)$. For even $n_c$, the static structure factor exhibits a peak at a temperature below the corresponding spin gap. Results for isotropically coupled ladders ($J_{bot}/J_{|} = 1$) are compared to those for the single chain and the square lattice. For $J_{bot}/J_{|} leq 0.5$, the correlation function of the two--chain ladder is in excellent agreement with analytic results from conformal field theory, and $xi(T)$ exhibits simple scaling behavior.
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