As the closing event of an exhibit which has been on display at Vose Library since January, the library and Union Historical Society will co-host a slide presentation of early 20th century images of Knox County scenes and locations at 7:00 p.m. on Thursday May 9 in the Old Town House, Town House Road, Union. Kevin Johnson, photo archivist for the Penobscot Marine Museum in Searsport, will present the slides and tell about the photos in the Eastern Illustrating & Publishing Co. Collection. The Eastern Illustrating & Publishing Co. was founded in 1909 by Rudolph Herman Cassens, a native of Rockland. Cassens’ goal was to photograph small towns and rural areas from Maine to California, producing postcards that would be valued for promoting tourism. In 1916, Maine’s Governor Oakley C. Curtis proclaimed April 19 to be Postcard Day. He asked every Maine resident to mail six postcards to friends and family, urging them to visit Maine for a vacation. Cassens never got beyond his original focus on Maine and the rest of New England and upstate New York, but his company produced over 40,000 glass plate negatives for “real photo postcards” from 1909 to the early 1950’s, at its headquarters in Belfast. Now enlarged, mounted and framed, the Knox County images are fascinating and take viewers back in time.