One-dimensional isomorphous inorganic polymers containing Anderson type heteropoly anion as a basic building unit, namely [La(H₂O)₇Cr(OH)₆Mo₆O₁₈]$_n$·4nH₂O (1), [Gd(H₂O)₇Cr(OH)₆Mo₆O₁₈]$_n$·4nH₂O (2), [Gd(H₂O)₇Al(OH)₆Mo₆O₁₈]$_n$·4nH₂O (3), and [Eu(H₂O)₇Al(OH)₆Mo₆O₁₈]$_n$·4nH₂O (4) have been synthesized and studied by the powdered X-ray diffraction, TGA, IR, electronic and ESR spectroscopy, and unambiguously by single crystal X-ray crystallography. Isomorphous compounds 1-4 are crystallized in orthorhombic system with $Pca2_1$ space group. The crystal structure analysis reveals a one-dimensional extended chain in which the Anderson type heteropolyanion, acting as the building unit, is linked by rare earth metal ions in a zig-zag fashion. In the crystal structure, all types of oxygens of the heteropolyanion, lattice waters, lanthanum coordinated waters are extensively involved in O—H…O hydrogen bonding interactions. Compounds are additionally characterized by UV-visible and ESR spectroscopy.