> I was wondering if mid-June will be busy enough

In 2011, recreational visitation to Badlands National Park by month went like this (in thousands):
April - 21
May - 59
June - 169
July - 217
August - 188
September - 116
October - 41
This means June is one of the larger monthly visitation months.

The problem is what constitutes "enough." One of the main appeals of Badlands, particularly its longer hikes, is its emptiness and lack of visitation. There's no guarantee that a hike you might want will have people on it, but also little reason to think an empty trail will have people you don't want to meet. All I can suggest is to drive to the trail head of a hike that interests you. If there's lots of cars, it's likely safe "enough" for you. If there's no cars (a distinct probability), it's also probably safe.

But, unfortunately, isolation is one of the inevitable facts of solo hiking. There's no guarantee that any trail will be free of dangers, either human or other.

Many trails I've been to throughout the country have sign in and out logs at the beginning. I would also leave an itinerary with someone back home and you can check in each night to let them know you finished safely. If they don't hear from you, they call local authorities.

oh, and if you are being really adventurous, you could do something like this:

http://www.findmespot.com/en/

i'm watching a co-worker bike across the country with that right now.

There will be plenty of people at Mt. Rushmore and Devils Tower. Both are fairly small monuments so you'll almost certainly be within eyesight and earshot of numerous people at all times.

Badlands and Custer are much bigger. If you're concerned about people, my best advice is to carry mace or something like that, and keep it readily accessible. Doesn't do any good in the bottom of your backpack or inside a zippered pouch, it needs to be in your pocket or on the strap of your backpack so you can grab it in an instant.

Personally I don't like sign in/sign out logs - while they are nice for authorities, they also advertise to anyone and everyone who is on the trail and how big their group is. Perfect way to let someone know that you are hiking alone - not exactly ideal if you are concerned about being attacked.

In general, the longer the trail and the further you are from the trailhead, the less likely you are to be attacked by a person. Nobody wants to hike 10 miles just to attack you, they're more likely to do it on a relatively short, unpopular trail. And Badlands is relatively desolate so there aren't many hiding places, making it unlikely that someone would try anything there.

The advice to leave your daily plans with someone is good, although it won't help you in the moment. But if you do get into trouble at least the authorities have an idea where to look.

Lastly, it is highly unlikely you will have any issues with people. It's very rare for anyone to be attacked in a national park, the times it does happen are generally well-publicized due to being so unusual. I would just take basic precautions, be smart and enjoy the trip.

Sylvan Lake in Custer State Park has well-traveled hikes: around the lake, Harney Peak, Sunday Gulch, with Cathedral Spires & Little Devil's Tower nearby. You can hike in the Needle's Eye area, which is busy. The hike around Legion Lake is also nice.

There should be no problem with the Devil's Tower WY trail around the base. Also on the way or on the way back, Spearfish Canyon has the Spearfish Falls trail behind the Lodge & Roughlock Falls trail, both are busy trails.

I feel a little more hesitant about hiking alone in the Badlands, not so much creeps, but heat, possible poor cell phone reception & more rattlesnakes. There are a couple shorter hikes just off the main road.

Enjoy your trip.

Thanks everybody! For the notch trail, how far a walk is it before reaching the ladder? I really want to climb it.

> how far a walk is it before reaching the ladder?

According to
http://www.protrails.com/trails/view/194
you reach the ladder after hiking .3 mile.