
I don't know much about Union Magazine specifically. There were many flash in the pan publications around this era when publishers realized that ~ wow ~ based on the success of Godey's, it was apparent that women liked to read! And so the market was full of magazines to appeal to women mostly of a privileged class, though cheaper books were likewise produced in an attempt to appeal to women of lower means as well. The glut would eventually lead to a magazine Darwinism, with the strong rising to the top and the weaker falling away. Godey's would likewise continue to dominate despite competition from Demorest's magazine, and would only eventually succomb to the popular format of Harper's Bazaar.