In Anthony Burns, by Virginia Hamilton, what does "Anthony Burns became a symbol of freedom" mean?It's from the book "Anthony burns: the defeat and...

What this line means is that Anthony Burns's case came to
represent, in the minds of many in the North, the desire that slaves had to be
free.

Anthony Burns was a slave who escaped to the North
when he was 19 years old.  One year later, he was captured in Boston and was tried under
the Fugitive Slave Act.  Burns was found to be a fugitive slave and was returned to the
South by force.  When this happened, Burns became a symbol.  Abolitionists in the North
used him as an example of the injustice of the Fugitive Slave Act.  Burns came to
represent the idea that it was horrible to take a person who had escaped from slavery
and then send him back to that terrible condition.

This is
why Anthony Burns became a "symbol of freedom" overnight.