The United States might be largely considered a meat-and-potatoes nation, but we sure do love our pizza.

Americans are expecting to spend nearly $45 billion on the pies this year, according to pizza industry trade analysis, but while we're united on our love of pizza, we're divided on where to get it from.

There are approximately 70,000 pizzerias around the country, more than half of which are affiliated with the top chains. And just as there are iconic styles of pizza, like New York and Chicago, there are iconic companies who make them.

To get a sense of how true icons of the pizza industry continue to expand their slice of the $45 billion pie — and how a new group of pizza chains are becoming iconic in a hurry — we've compiled a list of the chains that have the highest annual sales and are also seeing tremendous growth, as well as pizza companies that have seen a recent surge in popularity, measured by year-over-year sales growth.

The undeniable king of U.S. pizza, this Plano, Texas-based chain, part of Yum! Brands, hauled in gross sales of $13.4 billion last year, according to Pizza Today, and has more than 16,000 locations in 95 countries (including roughly 1,900 in China). For most of its early history, customers would flock to the red-roofed dine-in locations, but in the mid-'80s, Pizza Hut pivoted and began to focus more heavily on delivery and takeout to remain competitive.

It never rests in trying to reach a younger, more global and tech-first audience with special promotions: Pizza Hut just unveiled the first-ever playable DJ pizza boxes, a year after cooking up a box that turned into a movie projector.

Arguably the company that popularized home delivery of pizzas, Domino's had global retail sales of $8.9 billion last year. It operates 12,600 stores in more than 80 countries and delivers more than 1 million pizzas per day (but sells the most on Halloween, its busiest delivery day of the year). The company has been diversifying its menu: 70 percent of the items weren't available at the beginning of 2008.

It has also been making an effort to keep up with the tech times. Domino's recently launching a zero-click order feature that counts down 10 seconds from the time you open the mobile app to order your favorite pizza or previous order. It also includes a GPS feature so the pizza isn't put in the oven until the customer is close to the store.

Digital sales now account for more than half of Domino's sales, and its CEO said that's a reason why it is growing at a time burger chains are slowing down. Its CEO also recently told CNBC that it is exploring the use drones and autonomous vehicles to deliver pizza. Investors have noticed: Domino's stock is up near-500 percent in the past five years.

Famously started in 1984 when founder John Schnatter sold his Z28 Camaro to purchase pizza-making equipment, Papa John's has grown into one of the world's largest pizza chains. Last year it had gross sales of $3.3 billion, and it currently has nearly 4,900 locations in the United States and 39 other countries. It also has some high-profile franchisees, including former Denver Bronco's quarterback Peyton Manning.

Like Domino's, the company's stock has been a big winner, up 450 percent in the past five years. McDonald's market gain in the past five years, as a reference point, is 32 percent.

The industry's third-largest chain takes a different model than most of its competitors. Rather than delivering pies to customers, it asks them to come to its stores. The hook, though, is the low price of the pizzas (a large pepperoni typically costs around $5) and the lack of wait time. Gross sales last year came in at $3.4 billion at its more than 4,000 locations.

Founded in 1995, Papa Murphy's takes an entirely different approach to serving pizza to customers. It has them make it at home themselves, also referred to as "take and bake" pizza. Unusual? Yes, but it also proved to be a successful model that led to an initial public offering a few years ago. Not having to buy pizza ovens meant requiring less space, so the company could pass along savings to customers. System-wide sales last year topped $785 million, and the chain has grown to more than 1,500 locations in the United States and Canada.

But its market performance hasn't matched the recent run of Papa John's and Domino's stock: After reaching an all-time high last summer, its shares now sit at a 52-week low and have declined near-50 percent this year as sales growth has slowed. Same-store sales for Papa Murphy's fell by 4 percent in the most recent quarter, and the company projecting that sales growth will remain in decline for the rest of the year.

Loyal customers may still love the product, but a 50 percent drop is not what an investor wants to take home from a recent IPO.

Founded in 1991, Toppers is starting to dramatically expand its national footprint. The Wisconsin-based chain, which had sales of $39.5 million last year, opened its 75th location in 2015 and is now in 13 states. It expects to hit 100 stores by next year and is aiming for 700 locations by 2025. Technomic, in its annual Top 500 Chain Restaurant Report, noted the company saw some of the biggest sales surges of any pizzeria last year.

Ranked by Pizza Today as one of the top 10 chains in the country, Marco's was another restaurant Technomic cited as having a big sales surge last year. With gross sales of $380 million (up from $315 million in 2014), the company opened 113 new stores last year, bringing its total to more than 700 in the United States. It expects to have 1,000 locations by the end of 2017.

It claims to be "the fastest-growing pizza company in the U.S." based on the number of stores signed into development since 2007.

This five-year-old California-based chain touts NBA all-star LeBron James as one of its investors. Its hook: an assembly-line approach to making pies to order, with healthy, artisanal ingredients and a cook time of less than 3 minutes. Privately held, it does not release earnings, but Technomic says sales were up 205 percent last year. It currently has 124 locations in 28 states (and Canada).

According to Technomic, MOD was the country's fastest-growing restaurant chain (in any category) last year, with sales increasing 220 percent from the previous year. (The group does not give specific sales numbers.) Privately held, the fast-casual pizza restaurant has 100 locations in 16 states and focuses on affordable food and paying employees well.

Like Blaze, Pieology lets guests customize their pies and see them cooked within 3 minutes. As a kicker, it also offers the chance to add after-bake sauces, such as buffalo or pesto. Pizza World reports Pieology had sales of $51 million last year, and in January the founders of Chinese fast-food chain Panda Express bought a minority stake in the company. Pieology currently has nearly 100 locations, with the majority of its locations in California.

Correction:
This story was updated to reflect that Toppers had sales of $39.5 million in 2015.