Neoclassicism was a widespread and influential movement in painting and the other visual arts that began in the 1760s, reached its height in the 1780s and '90s, and lasted until the 1840s and '50s. In painting it generally took the form of an emphasis on austere linear design in the depiction of classical themes and subject matter, using archaeologically correct settings and costumes.
Instead of the excessivly pompous Rococo style, simplicity, geometry and symmetry featured in the new style. Neoclassicism was given great impetus by new archaeological discoveries, particularly the exploration and excavation of the buried Roman cities of Herculaneum and Pompeii (the excavations of which began in 1738 and 1748, respectively).
Neo-classicism was a child of the Age of Reason (the Enlightenment), when philosophers believed that we would be able to control our destinies by learning from and following the Laws of Nature (the United States was founded on Enlightenment philosophy). Scientific inquiry attracted more attention. Therefore, Neo-classicism continued the connection to the Classical tradition because it signified moderation and rational thinking but in a new and more politically-charged spirit (“neo” means “new,” or in the case of art, an existing style reiterated with a new twist.)
Neo-classicism is characterized by: clarity of form; sober colors; shallow space; strong horizontal and verticals that render that subject matter timeless, instead of temporal as in the dynamic Baroque works; and, Classical subject matter—or classicizing contemporary subject matter.