Question: The 1939 New York World's Fair was exceedd in expanse only by another fair which was held in St. Louis , Missouri during what dates?

Context paragraphs:
IND World's Fair Line: The IND World's Fair Line, officially the World's Fair Railroad, was a branch of the Independent Subway System (IND) serving the 1939 New York World's Fair in Queens, New York City.  It split from the IND Queens Boulevard Line at an existing flying junction east of Forest Hills–71st Avenue station, ran through the Jamaica Yard and then ran northeast and north through Flushing Meadows–Corona Park (roughly where the Van Wyck Expressway is now) on a wooden trestle to the World's Fair Railroad station, a bit south of Horace Harding Boulevard (now the Long Island Expressway).  The World's Fair station was the only one on the line.

The Middleton Family at the New York World's Fair: The Middleton Family at the New York World's Fair is a 1939 American film directed by Robert R. Snody produced by Westinghouse for their exhibit at the 1939 New York World's Fair.

Louisiana Purchase Exposition: The Louisiana Purchase Exposition, informally known as the St. Louis World's Fair, was an international exposition held in St. Louis, Missouri, United States, from April 30 to December 1, 1904.  Local, state, and federal funds totaling $15 million were used to finance the event.  More than 60 countries and 43 of the 45 American states maintained exhibition spaces at the fair, which was attended by nearly 19.7 million people.

Good Neighbor Policy and the 1939 World's Fair: At the 1939 World's Fair, the Good Neighbor policy was developed by encouraging cultural exchange between the United States and Latin American countries by cooperation in presenting the event.  The Good Neighbor policy was the foreign policy of the administration of United States President Franklin Roosevelt towards Latin America.  The 1939 New York World's Fair was a World's fair in New York.

R36 World's Fair (New York City Subway car): The R36 World's Fair (also known as R36 WF) or formerly known as the blue R36 New York City Subway cars, was a New York City Subway car that was built in 1963 and in 1964 by the St. Louis Car Company in St. Louis, Missouri for the IRT division (also known as the A Division).  They were purchased for service on the IRT Flushing Line ( trains) which was the closest line to the 1964 New York World's Fair.  These were the last entirely LAHT bodied (non-stainless) cars built for the New York City Subway.

Queens Museum: The Queens Museum, formerly the Queens Museum of Art, is an art museum and educational center located in Flushing Meadows-Corona Park in the borough of Queens in New York City, United States.  The museum is housed in the New York City Building, which was built for the 1939 New York World's Fair, and which then hosted the United Nations General Assembly from 1946 to 1950.  The museum itself was founded in 1972, and has among its permanent exhibitions, the "Panorama of the City of New York", a room-sized scale model of the five boroughs originally built for the 1964 New York World's Fair, and repeatedly updated since then.  It also has a large archive of artifacts from both World's Fairs, a selection of which is on display.

Westinghouse Time Capsules: The Westinghouse Time Capsules are two time capsules prepared by the Westinghouse Electric & Manufacturing Company: "Time Capsule I" was created for the 1939 New York World's Fair and "Time Capsule II" was created for the 1964 New York World's Fair.  Both are buried 50 feet below Flushing Meadows–Corona Park, the site of both world's fairs; the 1965 capsule was placed ten feet north of the 1939 capsule.  The capsules are to be opened at the same time in the year 6939, five thousand years after the first capsule was sealed.

Symphony No. 7 (Bax): The Symphony No. 7 by Arnold Bax was completed in 1939 and dedicated to "The People of America".  The work received its first performance in Carnegie Hall, New York City, by the New York Philharmonic on 10 June 1939 under the baton of Sir Adrian Boult.  It was commissioned by the British Council to be played at the 1939 New York World's Fair, along with Arthur Bliss's Piano Concerto in B-flat, and Ralph Vaughan Williams' "Five Variants of Dives and Lazarus".

Saint Louis Exposition: The Saint Louis Exposition or St. Louis Expo was a series of annual agricultural and technical fairs held in St. Louis' Fairgrounds Park, from the 1850s to 1902.  In 1904, the Louisiana Purchase Exposition, a major World's Fair, was held in St. Louis, Missouri, United States.  The annual agricultural/technical exposition was not held in 1903-4, and ceased after the World's Fair.  It is easy to confuse memorabilia from the annual St. Louis Expositions with 1904 World's Fair memorabilia.

1939 New York World's Fair: The 1939–40 New York World's Fair, which covered the 1216 acre of Flushing Meadows-Corona Park (also the location of the 1964–1965 New York World's Fair), was the second most expansive American world's fair of all time, exceeded only by St. Louis's Louisiana Purchase Exposition of 1904.  Many countries around the world participated in it, and over 44 million people attended its exhibits in two seasons.  The NYWF of 1939–1940 was the first exposition to be based on the future, with an opening slogan of "Dawn of a New Day", and it allowed all visitors to take a look at "the world of tomorrow".  According to the official New York World's Fair pamphlet:

Supporting paragraphs: 1939 New York World's Fair Louisiana Purchase Exposition
Answer: April 30 to December 1, 1904