Which US President, despite serving only a single term, significantly expanded national parks and forests, faced challenges due to a major economic recession, and championed conservation efforts that earned him the nickname 'The Great Conservationist'?

1. He signed the Antiquities Act of 1906.
2. His successor later split with him and ran against him.
3. He was known for his 'Square Deal' domestic policy.
4. He served as a Rough Rider during the Spanish-American War.