The designation of the oldest synagogue in the United States requires careful use of definitions, and must be divided into two parts, the oldest in the sense of oldest surviving building, and the oldest in the sense of oldest congregation. Even here, there is the distinction between old synagogue buildings that have been in continuous use as synagogues, and those that have been converted to other purposes, between buildings that have been in continuous use as synagogues and those, such as the Touro, that were shuttered for many decades, and between early established congregations that have been in continuous existence and early congregations that ceased to exist.
All of the oldest congregations in the new world were founded by Sephardi Jews and followed the Sephardic liturgy.
Until 1795, all congregations in the United States were Sephardic, although many or even most of the members of these congregations were descended from Eastern European Jews.
This list includes only buildings that are still standing. Some are still in use as synagogues, others have been repurposed.
Reform Congregation Keneseth Israel is the sixth oldest Reform Jewish synagogue in the United States. It began in Philadelphia in 1847, and was at a number of locations in the city before building a massive structure on North Broad Street in 1891. In 1900 KI, as the Congregation is known, was one of the largest Reform Congregations in the United States. In 1957 the congregation completed the move to Elkins Park, a suburb north of Philadelphia. The new building incorporated many of the stained glass windows that had been in the Broad street building, including the commemorative window installed under the leadership of Rabbi Krauskopf after the death of his friend Theodore Roosevelt. The building also included a newly created series of windows by the well known artist Jacob Landau (which are discussed below). The move to Elkins Park reflected the growing suburbanization of American Jews in the post-War period.
In 1847 Julius Stern led in the creation of Keneseth Israel as a traditional German –Jewish Congregation. Stern and 47 other men seceded from an existing synagogue, Congregation Rodeph Shalom (the 3rd oldest in Philadelphia), to create the new congregation. Until the 1880s business meetings were conducted in German, and services were in both German and Hebrew. The new Congregation's ritual was initially based on traditional, Orthodox Jewish customs and practice. When first organized the synagogue hired a lay "reader," B.H. Gotthelf, rented space, and made plans to have burial plots in a local cemetery. The congregation established its first religious school 1849, with about 75 children learning Hebrew and Jewish ritual. 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. At about this time the congregation also adopted the recently published Hamburg Prayer Book, which came out of the new Reform Movement in Germany. In 1854 KI purchased its first building, a former church on New Market Street, which was rededicated and consecrated as a synagogue. The re-purposing of religious edifices is common in America, as new immigrants acquire buildings that were built by other faiths. While KI did not yet have an ordained rabbi, Orthodox rabbis from other Congregations in Philadelphia participated in the re-consecration of the building.