  Short length quantum wires (quantum contacts) exhibit a conductance structure
at the value of conductance close to 0.7 \times 2e^2/h. The structure is also
called the conductance anomaly. In longer contacts the structure evolves to the
lower values of conductance. We demonstrate that this structure is related to
the development of charge density waves within the contact. This is a precursor
for Wigner crystallization. Many-body Hartree-Fock calculations of conductance
are performed. The results are in agreement with experimental data.
