Which U.S. President advocated strongly for the preservation of the Grand Canyon?

The correct choice is Theodore Roosevelt, who is well-known for his strong advocacy for conservation and the preservation of natural resources in the United States. During his presidency, which lasted from 1901 to 1909, he took significant steps to protect the Grand Canyon from potential encroachment by developers and industrial interests. He established the Grand Canyon National Monument in 1908, which played a crucial role in safeguarding the area and its unique natural beauty. Roosevelt's appreciation for nature was reflected in his broader environmental policies, leading to the establishment of numerous national parks, forests, and monuments. His commitment to conservation has had a lasting impact on the preservation of America's natural heritage.

In contrast, other Presidents mentioned in the options did not have a specific focus on the Grand Canyon or did not take significant actions towards its preservation. Lincoln, for instance, is associated with the preservation of the Union and the abolition of slavery rather than environmental issues, while Jefferson's contributions were primarily in the realm of expansion and governance rather than direct conservation efforts. Roosevelt’s profound legacy in environmental activism distinguishes him as the key figure in the preservation of the Grand Canyon.