What was the last colony to be founded and was designated as a royal colony?

The last colony to be founded and designated as a royal colony is Georgia. Established in 1733, Georgia was created as a social experiment to provide a fresh start for debtors and the poor from England, as well as to serve as a buffer against Spanish Florida and French Louisiana. Originally, it was a trusteeship, meaning it was governed by a group of trustees rather than a royal governor. However, in 1752, Georgia transitioned to a royal colony after dissatisfaction with the original trustees and their governance. This designation gave the British Crown direct control over the colony's government.

While Delaware, New Jersey, and New Hampshire were important colonies, they were established much earlier and did not undergo the same transition to royal status in the context described. Therefore, understanding the role of Georgia within the framework of colonial America highlights its unique status both in terms of founding and governance, affirming its place as the answer to the question.