Pope Francis made a historic visit to the United States Congress during his visit to Washington, D.C., on Thursday. He spoke to a joint session of Congress on a range of important subjects including immigration, poverty, climate change, and the death penalty.

The pope's speech was marked by humility and compassion, as he addressed contemporary global and domestic issues through a historical lens. In his speech he evoked four exemplary American figures: President Abraham Lincoln, civil rights leader Martin Luther King, Jr., and social activists Dorothy Day, and Thomas Merton.

Here were the four most important moments of the Catholic Church leader's remarks to the joint session of Congress:

1. Climate Change

Climate change and the environment were two topics that caused commotion in the run up to the pope's address—even causing one Arizona Republican to boycott the speech on the grounds that liberal-inflected climate change talk was out of bounds in Catholic doctrine.

The pope told congressional leaders that now was the time to act on reversing the course of man-made climate change, framing the issues of a changing planet as a "common good" interest.

"This common good also includes the earth, a central theme of the encyclical which I recently wrote in order to 'enter into dialogue with all people about our common home,'" he said. We need a conversation which includes everyone, since the environmental challenge we are undergoing, and its human roots, concern and affect us all."

"I call for a courageous and responsible effort to 'redirect our steps', and to avert the most serious effects of the environmental deterioration caused by human activity. I am convinced that we can make a difference and I have no doubt that the United States—and this Congress—have an important role to play."

2. Death Penalty

In perhaps one of the more surprising moments, Pope Francis addressed a global need for the abolition of the death penalty. His comments followed an introduction framed by the so-called "Golden Rule," during which he also noted the need to "protect and defend human life at every stage of its development." But the pope's brief reference to abortion was far overshadowed by his statements on abolishing capital punishment.

"I am convinced that this way is the best, since every life if sacred, every human person is endowed with an inalienable dignity, and society can only benefit from the rehabilitation of those convicted of crimes. Recently my brother bishops here in the United States renewed their call for the abolition of the death penalty. Not only do I support them, but I also offer encouragement to all those who are convinced that a just and necessary punishment must never exclude the dimension of hope and the goal of rehabilitation."

3. Immigration

Addressing recent political disputes over immigration in the U.S., the pope framed the issue as part of America's historical and contemporary immigrant fabric.

"In recent centuries, millions of people came to this land to pursue their dream of building a future in freedom. We, the people of this continent, are not fearful of foreigners, because most of us were once foreigners. I say this to you as the son of immigrants, knowing that so many of you are also descended from immigrants."

Pope Francis told gathered members of Congress that because early immigration to the country was often marked by turbulence and violence, current immigration calls for inclusion, understanding, and acceptance. He asked whether South and Central American immigrants moving north in search of a better life was not in the same interests of "our own children."

"Those first contacts were often turbulent and violent, but it is difficult to judge the past by the criteria of the present. Nonetheless, when the stranger in our midst appeals to us, we must not repeat the sins and the errors of the past. We must resolve now to live as nobly and as justly as possible, as we educate new generations not to turn their back on our “neighbors” and everything around us. Building a nation calls us to recognize that we must constantly relate to others, rejecting a mindset of hostility in order to adopt one of reciprocal subsidiarity, in a constant effort to do our best."

On the subject of immigration, the pope addressed the recent refugee crises in Europe and elsewhere ,caused by unrest in the Middle East and North Africa. He urged compassion for those seeking a better life, and reiterated the reciprocal principles of the Golden Rule. "We must not be taken aback by their numbers, but rather view them as persons, seeing their faces and listening to their stories, trying to respond as best we can to their situation," the pope stated. "To respond in a way which is always humane, just and fraternal."

4. Inequality

Francis called for a consolidated effort to combat times of crisis and economic hardship for many of the world's citizens, driving home the need for a constant fight against poverty and hunger.

"How much progress has been made in this area in so many parts of the world! How much has been done in these first years of the third millennium to raise people out of extreme poverty! I know that you share my conviction that much more still needs to be done, and that in times of crisis and economic hardship a spirit of global solidarity must not be lost. At the same time I would encourage you to keep in mind all those people around us who are trapped in a cycle of poverty. They too need to be given hope. The fight against poverty and hunger must be fought constantly and on many fronts, especially in its causes. I know that many Americans today, as in the past, are working to deal with this problem."