We study the Wigner crystallization in semiconductor quantum wires within the density-functional approach. As the density of electrons in quasi-one-dimensional structures is lowered, we find that the system favors the crystalline phase as envisioned by Wigner. The dependence of the critical density on the lateral width of the quantum wire is also investigated. In a structure consisting of two parallel quantum wires, the Wigner transition to the solid phase is enhanced similarly to the bilayer systems.