As you can see, there are a lot of bands on this bill. And advertising that many acts is inherently text-heavy, making for some difficult and unwieldy design. That's why it is all the more impressive that this flier comes out looking so good.
The first key to its success is the use of an iconic image. In that simple line-drawing of hands lighting off fireworks, it manages to summon a boatload of summer memories, setting the tone perfectly. Apart from the Uncle Sam image, nothing says "Fourth of July weekend" like fireworks, and fireworks don't carry the same political baggage that Uncle Sam might.
The real trick is getting all that type to work without looking cluttered and the designer is to be lauded for pulling it off. The choice of a sans serif font might be intuitive, but the choice to alternate the colors (and the subdued color palette used) is inspired. It lets the flier cram a lot of info into as small an area as possible and keeps it from being too busy. That's good design.
There are some other nice touches, such as the distressed effect on the type and the wise use of different font sizes to display the various classes of information, but the bottom line here is the design doesn't take the easy way out. For fliers like this, the temptation must be mighty to simply throw up your hands at the impossibility of fitting so many band names and other info into a confined space, and cop out by just making a list of bands and hoping it "sells itself." This designer didn't do that and the elegant solution they came up with is both functional and attractive. Kudos.