Rabbi David Einhorn was the most prominent Jewish opponent of slavery when the Civil War began, and from that point on KI was known as the "Abolitionist Temple."

In 1852 the congregation began to have sermons, which was a step away from traditional Orthodox Jewish ritual, but reflected the common Protestant worship that dominated the United States.

After moving into its new building KI quickly purchased an organ, which marked its movement away from traditional orthodox Judaism, which did not have musical instrument or choirs at its services.

Although Deutsch was not an ordained rabbi, he moved KI further along on its road to Reform observance, by, among other things, abolishing separate seating for men and women, which is an obvious marker of the difference in worship between Orthodox synagogues and others in the United States and elsewhere.

KI dismissed Deutsch in 1860 but the following year hired David Einhorn, an ordained Rabbi, who was one of the most prominent Reform leaders in the United States.

That year he published a 64-page prayer book pamphlet, for the use on Shabbat (the Jewish Sabbath) and for the three Biblical festivals, Sukkot, Passover, and Shavuot.

But at the same time he claimed that "as a teacher in Israel" his role was "not to place before you my own feelings and opinions, but to propound to you the word of God, the Bible view of slavery.

Incensed, Einhorn delivered an antislavery sermon in German, and then published an English translation in his monthly journal Sinai,[11] refuting the Raphall's pamphlet.

Einhorn's last paragraph (see box quote below) was about the relationship between ethics, religion, and the Bible: This publication was both morally righteous and political dangerous.

In 1857 the Congregation had protested a treaty with Switzerland which was supposed to give citizens of both countries equality in travel and business opportunities, but in fact allowed Swiss Cantons to discriminate against American Jews.

In 1875, at the age of 17, Krauskopf went to Cincinnati, where he was a member of the first class at the Reform Movement's recently opened rabbinical school, Hebrew Union College (HUC).

In 1892 KI moved to a brand new building on North Broad Street (built under Krauskopf's leadership), with a sanctuary that provided seating for 1600 people.

Throughout his tenure at KI Krauskopf gave weekly Sunday lectures to overflow crowds on history, science, ethics, politics, economics, theology, and the Bible.

In 1888, shortly after he arrived in Philadelphia, Krauskopf was instrumental in the creation of the Jewish Publication Society,[26] with KI giving early support the endeavor.

Beyond the Synagogue, Krauskopf worked with religious leaders of other faiths, visited Russia to investigate discrimination and violence against Jews, and raised money for the creation of the National Farm School, which more than a century later became Delaware Valley University.

Shortly after the outbreak of the Spanish–American War in 1898, Krauskopf became a leader of the National Relief Commission, and was one of three special field commissioners sent to visit army camps in the United States and Cuba.

Krauskopf's and KI's military and patriotic support continued during World War I when the congregation created special programs for servicemen stationed in Philadelphia or passing through the city on their way to the front.

This was a gesture of reverence for the spiritual leader who had made KI one of the most prominent and important congregations in the national reform Jewish world.

He was strong advocate of women's suffrage and spoke out against lynching, and despite threats on his life, regularly denounced the Ku Klux Klan.

Before large crowds he gave lectures in support of the right to study evolution, but shortly after he left Tennessee the state passed its infamous anti-evolution law that led to the Scopes "Monkey" Trial.

He consistently argued that Jews were members of a religion, not a nationality, and thus KI accepted the formal position of the Reform Movement (as expressed through the Union of American Hebrew Congregations) to "disassociate itself completely from any controversy pertaining to political Zionism."

He reintroduced Bar and Bat Mitzvah, Torah reading on Saturday and the Jewish High Holidays (Rosh Hashanah and Yom Kippur), restored the position of cantor, and added violin or cello to the congregation's musical services.

During World War II KI provided worship services for thousands of soldiers and sailors who were stationed in Philadelphia, or passed through on their way to other posts.

Organizations within KI (such as the Sisterhood and Men's Club) were involved in blood drives, the preparation of bandages, and the writing of letters to soldiers overseas.

Bertram Korn, who had his Bar Mitzvah in KI when Fineshriber reintroduced the ceremony, enlisted as a chaplain in the Navy during the war, serving with the 1st and 6th Marine Divisions in China.

At the end of the war, Fineshriber, as a national leader of the reform movement, opposed the creation of a Jewish state in British Palestine, which became Israel in 1948.

In 1957, under Rabbi Korn's leadership, KI moved from its Broad Street location to a new building at the current address on Old York Road in Elkins Park, Pennsylvania.

"The Prophetic Quest"[28] is the title of the ten stained glass windows designed by Jacob Landau and installed in the KI synagogue[29] in Elkins Park, Pennsylvania in 1974.

The director/curator, as-well-as the volunteers, include in their museum tours the collection of stained glass windows "The Prophetic Quest" by Jacob Landau.

Like Rabbi's Krauskopf and Korn, Sussman was active in the movement to help Jews escape the Soviet Union and more recently has been involved in efforts to reach out to the small Jewish community in Cuba.