Complex sentence: Senator Arthur V. Watkins of Utah, the strongest proponent for termination, equated it with the Emancipation Proclamation, which declared the freedom of all slaves in the territory of the Confederate States of America.
Split into simpler sentences: Senator Arthur V. Watkins of Utah, the strongest proponent of termination, equated it with the Emancipation Proclamation. That had declared the freedom of all slaves in the territory of the Confederate States of America.