In this series, we'll be hiking the burger trail to find the latest, greatest and most delicious burgers in Milwaukee. Click here for an explanation of the criteria used to rate each burger. Where have we been? Check out the complete catalog of burger reviews here.

It’s National Cheeseburger Day. So, there’s no better time to take a closer look at some of the top burgers we’ve encountered on the Burger Trail.

Over the past nine months, we’ve explored a variety of venues – from diners and dive bars to some of the city's more high end restaurants – in a search for the best burgers in the city. And we’ve found a good many favorites at old-school joints, most of which have been around for 50 years or more.

And there’s a reason why these burgers have stood the test of time. They might not be loaded with frills or special toppings. But, they’re well-executed burgers, made with quality ingredients, that all come with a big sloppy side of nostalgia.

To rate each of the burgers, we've developed a 50-point scale, with 10 points possible in each of five categories: presentation, bun/bread, burger, toppings and value. So, a burger's overall score is a compilation of ratings in each category.

Eager to try a great old school burger? Here's the five that top our list (in reverse order):

5. The Big Boy at Kil@wat  28/50

Big Boy might not be around anymore, but the classic burger has survived. At $12 the Big Boy burger felt a bit spendy for what it is: an old-school diner burger with wilty lettuce, a soft bun and special sauce. It is, however, a good old-school diner burger that might bring back some memories for you if you recall the Marc's Big Boys of yore. And sometimes nostalgia is worth paying a bit more for.

4. The double cheeseburger at The Kiltie Drive-in  38/50

The Kiltie's double cheeseburger is as delicious as any in its camp. And at just over $5, it's a deal, even when you have to pay a bit extra for fries or onion rings. The lettuce was fresh, and the pickles were thick and crisp. The cheese was ample and well melted. Maybe most impressive was the thickly sliced tomato, which was flavorful and juicy. Read the full review.

3. The cheeseburger at Kewpee Sandwich Shop  38/50

At Kewpee's you'll find a solid, unpretentious burger that's served up with a smile, and a big fat nod to the past. If you don't specify otherwise, your cheeseburger comes topped with American cheese (that's been grilled, ensuring it's melty, melty, melty), pickles, raw onion (don't even ask for fried; it's not an option), ketchup and mustard. And that's just fine. In the end, it delivers the classic burger flavor that everybody wants. Even better, at $1.95 you can afford to get two. Read the full review. 

2. The cheeseburger at Nite Owl  40/50

Nite Owl’s hand-formed burger is thick and juicy and delightfully imperfect. The works gives you a generous dose of ketchup and mustard. There are sweet, soft, fried onions and an impressive stack of cheese which melts thoroughly and eagerly right down the sides of the burger.

Don't miss the opportunity to make a trek to Nite Owl during its operational months. After all, the burgers are delicious and the nostalgia is sweet. Read the full review. 

1. The cheeseburger at Mazo’s  40/50

When it came to the burger at Mazo’s, it was classic all the way. The beef patty is fresh, with great texture. There were just enough sweet, browned onions to offer a bit in every bite. Similarly, the perfectly melted cheese coated the burger, offering up that brilliantly salty umami flavor that only processed cheese can.

There's something to be said for a burger that stands solid, even without reliance on frills. In fact, it's likely the utter simplicity of the Mazo's burger that makes it a true Milwaukee classic. Read the full review. 

Is your favorite old-school burger on this list? If not, let us know where we can find it. Leave your recommendations in the comments or email me at lori@onmilwaukee.com.