Plz take a look at this..
Benjamin Lincoln, a Revolutionary War general, spoke for most Americans of his day when he observed in 1792, Civilization directs us to remove as fast as possible that natural growth from the lands.
Plz, explain the word of his day and observed in this sentence.
'His day' and 'observed' indicate Revolutionary War which he participated in otherwise observed means that just he spoke.

Question

Answer

The sentence is missing some punctuation, which makes it more challenging to read.
"of his day" - those who lived around the same time as him, in 1792.
"observed" - sometimes it means "looked at", but in this case it means "studied the situation and made a conclusion".