Founded as a Dutch Reformed Church in 1657, this congregation was one of seven that organized the first Presbytery in America in 1706. As English rule replaced Dutch, the congregation evolved alongside the town, transitioning from Dutch Reformed to Presbyterian as New Castle grew into the colonial capital. During the Revolution, its members were predominantly patriots, including Thomas McKean, a signer of the Declaration of Independence. The current brick meeting house, built in 1707 and beautifully restored, includes a cemetery and memorial garden with gravestones dating to the early 1700s that tell poignant stories of colonial life.

As English rule took hold after 1664, the Anglican Church established its first foothold in Delaware here on the Green. Immanuel is the oldest Anglican church in the United States with continuous Sunday services, its founding tied directly to New Castle's era as the colonial capital. Its churchyard is among the most historically significant in Delaware. The earliest stone belongs to Hercules Coutts, who died in 1707. Notable figures interred here include George Read, signer of the Declaration of Independence; George Read Jr., the first U.S. Attorney for Delaware; George B. Rodney, U.S. Representative; and Nicholas Van Dyke Jr., U.S. Senator. Mary Borden McKean, wife of Thomas McKean and 2nd Governor of Pennsylvania, also rests here.

By the early 19th century, New Castle was receiving waves of Irish and later Italian immigrants, and with them came the Catholic faith. Mass was first celebrated in New Castle in 1804 by Father Patrick Kenny, a Dublin-born priest who became a pioneering figure of Catholicism across Delaware. A wooden chapel followed in 1807, and the parish grew substantially over the following decades with the arrival of Irish and Italian immigrant communities. The current church, dedicated in 1876, remains an anchor of the historic district, and its burial history reflects the immigrant working families who helped build 19th-century New Castle.

Bethany UAME is a monument to one of the most significant acts of religious independence in American history. Founded by free African American Peter Spencer, the Union Church of Africans was the first independent African American religious denomination in the United States. Spencer and William Anderson led some forty African Americans out of a predominantly white Methodist church in Wilmington in 1805, with racial discrimination and the desire for Black religious independence at the heart of the secession. Bethany's New Castle congregation organized in 1815, beginning with prayer meetings in private homes before purchasing their first church site in 1818. The church and its burial ground remain testaments to the faith and resilience of New Castle's early African American community.

Methodism arrived in New Castle on the heels of the Revolution, carried by circuit-riding preachers spreading the faith across the new nation. The congregation traces its origins to visits by pioneering clergymen such as Thomas Webb and Francis Asbury before the American Revolution. By 1819 a group was meeting regularly in members' homes, and in 1820 they purchased land and erected a small brick chapel — now enclosed within the adjoining graveyard. Then known as Nazareth Methodist Episcopal Church, it served the community until the present church was built in 1863. That original chapel, now part of the graveyard, is one of the town's most quietly enduring landmarks.

In 1854, a Methodist Society was organized within New Castle's African American community. This was the era of rising tensions over slavery — New Castle's own courthouse had hosted the landmark trials of abolitionists Thomas Garrett and John Hunn just years prior — and Mount Salem became a pillar of strength for its congregation. The first members built the original church in 1878, carrying bricks to the site by hand, and the congregation later opened one of New Castle's first community centers during the Great Depression. The adjacent cemetery, expanded over generations, is the final resting place for families whose contributions to New Castle are as essential as any found in the town's more celebrated landmarks.