Answer the following question: What were the last names of the people who agreed to work together on the The American Portrait Gallery?  Answer the above question based on the context below:  With lessons learned from the Sanderson series, Longacre proposed to issue his own set of biographies illustrated with plates of the subjects.  He was on the point of launching this project, having invested $1,000 of his own money (equal to $25,097 today) in preparation, when he learned that James Herring of New York City was planning a similar series.  In October 1831, he wrote to Herring, and the two men agreed to work together on The American Portrait Gallery (later called the National Portrait Gallery of Distinguished Americans), published in four volumes between 1834 and 1839. Herring was an artist, but much of the work of illustrating fell to Longacre, who traveled widely in the United States to sketch subjects from life.  He again sketched Jackson, who was by now president, as well as former president James Madison, both in July 1833. He met many of the political leaders of the day, who were impressed by his portraits.  Among these advocates was the former vice president, South Carolina Senator John C. Calhoun. In July 1832, Niles' Register described a Longacre engraving, "one of the finest specimens of American advancement in the art".Longacre had married Eliza Stiles in 1827; between 1828, when their daughter Sarah was born, and 1840, they had three boys and two girls.  Sales of the Gallery lagged due to the Panic of 1837; Longacre was forced to declare bankruptcy and travel through the southern and midwestern states, peddling his books from town to town, with his wife and elder daughter managing shipping and finances at home.  Later in 1837, he was able to return to Philadelphia and open a banknote engraving firm with partners, Toppan, Draper, Longacre & Co.  With great demand for engraving for notes being issued by state banks, the firm prospered, and had offices at 60 Walnut Street in Philadelphia and a branch at 1 Wall Street in New York.  According to Snow, Longacre was known as the best engraver in the country.
Answer:
Longacre