Popular Library

Popular Library is a New York paperback book company established in 1942 by Leo Margulies and Ned Pines, who at the time were major pulp magazine and newspaper publishers. The company's logo of a pine tree was a tribute to Pines, and another Popular Library signature visual was a reduced black-and-white copy of the front cover on the title page. A native of Malden, Massachusetts, Pines became the president of Pines Publications in 1928 and continued to lead the company until 1961. He was the president of Popular Library from 1942 to 1966 and its chairman from 1966 to 1968. Retiring in 1971, he continued to work as a consultant.

From the Wikipedia article “Popular Library”, licensed under CC BY-SA 4.0.

An imprint is a brand inside a larger publishing house, often with its own editors and list. Imprints of large groups usually acquire through literary agents; read recent titles to see whether your book fits the list, then target agents who sell to it.