Just wanted to update this.
I drove by on the highway on Wednesday and noticed that the gate was closed, so I decided to look at Google earth to see just where exactly I ended up on Monday. While I was looking, I noticed what appeared to be two houses behind the No Trespassing signs in my last picture. That got me really curious to know who the heck was living out there in the middle of nowhere. After some digging, I found that the houses are actually owned by the county. Checking property records, I found that the houses were purchased in 1996 from an estate. Apparently the houses and all of the surrounding land was owned by an elderly woman and once she died the county bought it and turned it into a preserve.
Well then, since it is a county owned preserve I wanted to know why there was a gate that had been closed and what the heck is the county doing with two houses? I called the county and finally got connected to the director in charge of the preserve. So it turns out that the gate is supposed to be open from dawn to dusk. However, it's been closed for the last few days because the ranger that lives in the house on the property (Ha! That's who lives there!) reported on Saturday that the bridge is ready to fall apart and needs to be replaced ASAP.
The director said that they are working to get the bridge done as fast as possible, since the ranger lives there with his family and needs to cross the bridge every day.
I knew that bridge looked sketchy!