why was thoreau put in jail

i think it was because of tax evasion

Yes, I think he refused to pay his taxes because he objected to some of the things (like war) that the taxes paid for.

I think Thoreau WANTED to go to jail. This was his way of drawing attention to the immoral taxes. Classic civil disobedience. Rosa Parks would have made Thoreau proud: she openly disobeyed the immoral "blacks in the back of the bus" law, went to jail, and the attention she drew to the issue sparked the Civil Rights movement.