The Erie canal was started in 1817 and was finished in 1825 at a length of 363 miles.
The declaration was a laundry list of affronts to the colonies by King George III, wherein Jefferson et.al. argued that since the monarchy did not treat the colonists like other Britons, the colonists had the right to form their own sovereign nation. It was also intended to justify this action to other monarchies to prevent them from helping Britain retain the colonies under the doctrine of Intervention. So it helped to justify the war domestically and internationally.
Congress has the power to establish post offices and post roads, issue patents and copyrights, fix standards of weights and measures, establish courts inferior to the Supreme Court, and
to make all laws which shall be necessary and proper for carrying into execution.