was charles carroll last to sign declaration?

Answer 1

I think you're confusing "last signer" with "last SURVIVING signer",
(Carroll died on November 14, 1832 at the age of 95.)
http://en.wikipedia.org/wiki/Charles_Carroll_of_Carrollton

On the other hand, Carroll signed the document on August 2, when most of the other delegates did.

So who WAS the last person to sign it?
There is some reason to think it was Thomas McKean. He appears to have done so a bit after the official printing of the document on January 18, 1777, perhaps even later that month.
http://en.wikipedia.org/wiki/Thomas_McKean#Continental_Congress_and_Declaration_of_Independence
http://experts.about.com/e/t/th/Thomas_McKean.htm
http://research.history.org/pf/signers/signatures.cfm

Oddly though McKean himself claims to have signed it shortly after most of the other delegates did in August 1776 (most signed it on August 2).
http://research.history.org/pf/signers/bio_mckean.cfm

If his story is true and there was a printing error, the last signature would be that of Matthew Thornton (of New Hampshire) in November 1776.
http://research.history.org/pf/signers/index.cfm

See also:
http://www.archives.gov/national-archives-experience/charters/declaration_history.html

Answer 2

I'm not sure if he was the last signer, but if you want to know more about the man...

Charles Carroll of Carrollton (September 19, 1737–November 14, 1832) was a lawyer and politician from Maryland who was a delegate to the Continental Congress and later a United States Senator. He was the last surviving and only Catholic signer of the Declaration of Independence.