In 1847, Brooklyn was a relatively new suburb of New York that was on the verge of explosive growth. In just two decades the population would grow from 30,000 to 295,000, making it the third-largest city in the nation.

Of 39 churches in the city, only one was Congregational. So when a group of Brooklyn businessmen planned to start a new church, they were interested in reports of an impressive young minister in Indianapolis. He came to New York and delivered the first sermon in the new Plymouth Church; that same trip, he preached at the prestigious Park Street Church in Boston, which sought to call him as associate pastor.

Beecher accepted the call of the 21-member Plymouth Church, and by the end of his first decade as pastor the church boasted 1,241 members (not including 346 names which had been dropped, for a total of 1,586 members). It had become the city's largest church, and for a time was the nation's largest.

By 1867, in a new sanctuary, as many as 3,500 persons would seek admission to a service, with police and ushers turning away hundreds every Sunday. Beecher encouraged church members not to return for Sunday evening services to leave room for visitors; besides, he would tell them, one sermon a Sunday was enough for anyone!

Beecher preached evangelistically, inviting listeners to trust in a God of love and mercy. His sermons reflected much of the romantic spirit of the Victorian era, in contrast to the strict Calvinism of his father's generation.

In one area, however, Beecher retained his Calvinist heritage: in the desire for social reform. Beecher became actively involved in various reform movements, from anti-slavery to woman's suffrage. He often used his pulpit to address such issues, as well as using his oratorical skills in purely political settings. At one point the Brooklyn pulpiteer was even discussed as a possible Republican vice-presidential candidate (he was active in national and state Republican activities during much of his career).

What made Beecher such a popular preacher? It was not a natural gift as a speaker; as a child, he was plagued by thick, indistinct speech. While at Amherst, a speech professor helped Beecher overcome those early problems and develop above-average speaking skills. Those skills were further refined in preaching efforts at scores of churches where he supplied or led revivals.

Unlike many sermons of the day, Beecher's messages were written simply and clearly. In his first pastorate, he began the practice of keeping a written record of his sermons, including noting the reason for presenting a particular sermon. Though he would later abandon the journal, the idea of focusing on a specific target for a sermon was one he would continue to develop. He would recall years later, in his first series of Yale lectures:

I studied the sermons (of the apostles) until I got this idea: that the apostles were accustomed first to feel for a ground on which the people and they stood together; a common ground on which they could meet. Then they heaped up a large number of the particulars of knowledge that belonged to everybody; and when they had got that knowledge, which everybody would admit, placed in a proper form before their minds, then they brought it to bear upon them with all their excited heart and feeling. That was the first definite idea of taking aim that I had in mind.