I recently added the below photo and caption to the Trombone History Timeline (19th century—2nd half). It features the famous conductor-composer John Philip Sousa with the US Marine Band. Several trombonists are pictured on the far right. Additional trombone connections include that fact that Sousa’s father was a trombonist, as well as Sousa’s longtime connection with legendary trombonist-conductor Arthur Pryor.
1892—San Francisco, California: A photograph of John Philip Sousa and the Marine Band includes trombones (see below image; public domain).