Answer:
Low celebrates the completion of the Brooklyn Bridge and the hard work that went into building it.
Explanation:
I say this because in the third sentence, "At last we all rejoice in the signal triumph" they are clearly celebrating the completion of the Brooklyn Bridge and the hard work that went into building it.
The Great Depression happened in the 1920's and 1930's due to many economic disasters such as the Market Crash in 1929 and bad mistakes by the President (Hoover)
