This document provides an overview of architectural periods and styles from the 18th to early 20th centuries. It discusses how periodization differs between countries and eras. The long 19th century saw a return to classical styles like Greek, Roman, and Renaissance as well as Gothic. Architects drew inspiration from archaeological findings but also sought a distinct style for their era. By the late 19th century, eclecticism emerged as architects combined elements from multiple historical styles. Theories of this period evolved over the 20th century.