Wordnet 3.0
NOUN (1)
1. 
 the largest city in Missouri; 
 a busy river port on the Mississippi River near its confluence with the Missouri River; 
 was an important staging area for wagon trains westward in the 19th century; 
[syn: Saint Louis, St. Louis, Gateway to the West]
WordNet (r) 3.0 (2006):
Gateway to the West
    n 1: the largest city in Missouri; a busy river port on the
         Mississippi River near its confluence with the Missouri
         River; was an important staging area for wagon trains
         westward in the 19th century [syn: Saint Louis, St.
         Louis, Gateway to the West]