Dear Ms. Brennan,
Thank you for posting your request to History Hub!
We located several references to trotting parks in historical issues of the Shenandoah “Evening Herald” that are available online via the Pennsylvania Newspaper Archive. Examples include this edition from June 24, 1899 and this edition from May 15, 1899. You may be able to find some helpful information in these and similar newspapers. “The Evening Herald” and other newspapers are also available online via the Library of Congress' Chronicling America website.
Next, we located several images related to the Brandonville Trotting Park that was located a few miles away from Shenandoah, PA. Plus, we located an online description of Early Horse Racing in Pennsylvania and a brief history of trotting parks and horse racing on the Stories from PA History website that might be of interest to you.
We suggest that you contact the Greater Shenandoah Area Historical Society and the Schuylkill County Historical Society to see if they can offer you any additional assistance, and finally, you may be able to find some relevant resources on FamilySearch’s website for Schuylkill County, Pennsylvania Genealogy.
We hope this information is helpful. Best of luck with your family research!
If you have not already done so, you might want to contact the Schuykill Co PA Historical Society Schuylkill County Historical Society – The Official Historical Society of Schuylkill County (schuylkillhistory.org)
The Pottsville Library also has quite a few links to historical books, maps, etc Genealogy and Local History Materials at the Pottsville Free Public Library (pottsvillelibrary.org)