In the early afternoon of May 8, 1846, 2,300 U.S. troops, escorting 300 wagons full of supplies, marched out of the thickets of thorny brush and onto the broad prairie known as Palo Alto. Across the field, where the road toward Matamoros once again entered the chaparral, some 3,200 Mexican soldiers lined up to block the way.

Palo Alto Battlefield is a National Historical Park at Brownsville, Texas. My son and I were vacationing on Thanksgiving break in November 2019.
When talking to family, my brother in law was telling me a story of a construction crew in the concrete plant next door to the park. The story goes, that they would come in early hours in the morning to start processing material for making concrete. While they are working, they have experience door and lights being affected.
I visited the Park and walked with my son. Here is a video with some experience with the EMF. At the park, there is no power source that would spike the EMF reader, and it follows us as we walked toward the battlefield line of the U.S. Army.
I am not sure what caused the EMF spikes. This is the only time we did get any readings, and we were more than halfway through the walk heading to the U.S. Army battle line. The Mexican Army battle line was closed for maintenance so we did not venture there.
Let us know what you do you think? Is this park haunted?