For the New Century Issue of the journal "Theroretical Chemistry Accounts" the advisory editors identified papers from the first century of theoretical chemistry and discussed their importance for the twentieth century with an eye towards the twenty-first century. Sixty-six such perspectives are published in the New Century Issue. To make this unique collection available to younger scientists for entertaining reading and re-reading of the original publications, the publisher decided to reprint a special edition of the issue. Perspectives.- Perspective on "Zur Quantentheorie der Spektrallinien".- A Perspective on "Volume and heat of hydration of ions".- Perspective on "Zur Quantentheorie der Molekeln".- Perspective on "Wechselwirkung neutraler Atome und homöopolare Bindung nach der Quantenmechanik".- Perspective on "Neue Berechnung der Energie des Heliums im Grundzustande, sowie des tiefsten Terms von Ortho-Helium".- Perspective on "Quantum mechanics of many-electron systems".- Perspective on "Quantentheoretische Beiträge zum Benzolproblem. I. Die Elektronenkonfiguration des Benzols und verwandter Beziehungen".- Perspective on "The activated complex in chemical reactions".- Cavity and reaction field: "robust" concepts. Perspective on "Electric moments of molecules in liquids".- Perspective on "The transition state method".- Perspective on "Conduction in polar crystals. I. Electrolyte conduction in solid salts".- Reaction rates in condensed phases. Perspective on "Brownian motion in a field of force and the diffusion model of chemical reactions".- Perspective on "The effect of shape on the interaction of colloidal particles".- Perspective on Norman Ramsey's theories of NMR chemical shifts and nuclear spin-spin coupling.- Perspective on "New developments in molecular orbital theory".- Perspective on "A molecular orbital theory of reactivity in aromatic hydrocarbons".- Perspective on "The spectra and electronic structure of the tetrahedral ions MnO 4 ? , CrO 4 ? , and ClO 4 ? ".- Perspective on "Equation of state calculations by fast computing machines".- Perspective on "Quantum theory of many-particle systems I, II, and III".- Perspective on "On the theory of oxidation-reduction reactions involvingelectron transfer. I".- Perspective on "Statistical mechanical theory of irreversible processes. I. General theory and simple applications to magnetic and conduction problems.".- Using classical mechanics in a quantum framework. Perspective on "Semiclassical description of scattering".- Chemical building blocks in quantum chemical calculations. Perspective on "The density matrix in many-electron quantum mechanics I. Generalized product functions. Factorization and physical interpretation of the density matrices".- Perspective on "Some recent developments in the theory of molecular energy levels".- Perspective on "The physical nature of the chemical bond".- Perspective on "An extended Hückel theory. I. Hydrocarbons".- Perspective on "Stereochemistry of polypeptide chain conformations".- Perspective on "Inhomogeneous electron gas".- Perspective on "Correlations in the motion of atoms in liquid argon".- Perspective on "Self-consistent equations including exchange and correlation effects".- Perspective on "Exchange reactions with activation energy. I. Simple barrier potential for (H, H2)".- Perspective on "On the correlation problem in atomic and molecular systems. Calculation of wavefunction components in Ursell-type expansion using quantum-field theoretical methods".- Multireference many-body methods. Perspective on "Linked-cluster expansions for the nuclear many-body problem".- Finding the way through intermolecular forces. Perspective on "Permanent and induced molecular moments and long-range intermolecular forces".- Perspective on "Molecular collisions. VIII".- Perspective on "Benzynes, dehydroconjugated molecules, and the interaction of orbitals separated by a number of intervening ? bonds".-Perspective on "Intermolecular orbital theory of the interactions between conjugated systems." I General theory; II Thermal and photochemical cycloadditions.- Two landmarks in polymer physics: the Edwards model and de Gennes' observation.- Perspective on "Ab initio calculation of force constants and equilibrium geometries in polyatomic molecules. I. Theory".- Perspective on "Semiclassical theory of atom-diatom collisions: path integrals and the classical S matrix".- Quantum wavepacket approach to chemical reaction dynamics. Perspective on "Dynamics of the collinear H
