  High-resolution thermal expansion measurements have been performed for
exploring the mysterious "structureless transition" in (TMTTF)$_{2}$X (X =
PF$_{6}$ and AsF$_{6}$), where charge ordering at $T_{CO}$ coincides with the
onset of ferroelectric order. Particularly distinct lattice effects are found
at $T_{CO}$ in the uniaxial expansivity along the interstack
$\textbf{\textit{c*}}$-direction. We propose a scheme involving a charge
modulation along the TMTTF stacks and its coupling to displacements of the
counteranions X$^{-}$. These anion shifts, which lift the inversion symmetry
enabling ferroelectric order to develop, determine the 3D charge pattern
without ambiguity. Evidence is found for another anomaly for both materials at
$T_{int}$ $\simeq$ 0.6 $\cdot$ $T_{CO}$ indicative of a phase transition
related to the charge ordering.

Strongly Correlated Electrons