Few things say summer like a road trip. Ever since the days of the Ford Model T, Americans have loved to hit the open roads that stretch from sea to shining sea — it's a national rite of passage. And from mountain roads to coastal highways, there's no shortage of fantastic road trip-worthy routes across the U.S.

Here are 10 of the best road trips in the U.S. that are perfect for summer. And we'll let you in on a little secret: Many of these routes are beautiful year-round.

If you start in the South

Overseas Highway: Florida

• Best time to go: Any time of year

This aptly titled highway crosses over the turquoise waters that separate the Atlantic Ocean from the Gulf of Mexico via 42 bridges, including the state's longest, the Seven Mile Bridge. The 100-mile journey is lined with palms, native flora and fauna, retro motels and kitschy shell shops.

The drive takes about six hours round-trip from Florida City. However, you can easily extend it by starting in Miami and heading 33 miles south to Homestead, where you can visit Everglades National Park, Knaus Berry Farm (which is open annually from November through mid-April) for cinnamon rolls and the Robert Is Here Fruit Stand for tropical provisions and smoothies. Then, meander down the coral cay archipelago to Key West.

Blue Ridge Parkway: Virginia to North Carolina

Spanning 469 miles from Virginia's Shenandoah National Park to Great Smoky Mountains National Park in North Carolina and Tennessee, the Blue Ridge Parkway is home to some of the oldest mountains in the world.

The area is lush and green from spring through summer and equally beautiful in autumn (especially from late October to mid-November), when the landscape is painted with fiery shades of red, yellow and orange.

Along the way, consider a stop in Asheville, North Carolina, a mountain town known for some of the best food and craft beer in the Southeast.

If you start in the Midwest

Route 66: Illinois to California

Best time to go: Spring through fall

Dating back to 1926, Route 66 is one of America's most legendary highways. In addition to having wide-open landscapes, it offers plenty of well-preserved historic sites and distinctive retro landmarks, such as the World's Largest Catsup Bottle in Collinsville, Illinois. In the 1940s and '50s, the 2,500-mile highway, which stretches from Chicago to Santa Monica, California, was considered the quintessential American road trip.

In Amarillo, Texas, road trippers can find the Cadillac Ranch art installation that features rows of graffiti-painted Cadillacs sticking rear-end-first out of the ground. Just a 12-minute drive from the Cadillacs, you can fill up on some exceptional brisket at Tyler's Barbeque.

The New Mexican and Arizonan sections of Interstate 40 (which partially replaced Route 66) are particularly picturesque and feature several notable landmarks, including Arizona's Jack Rabbit Trading Post, which has been a popular pit stop for travelers for more than a half-century. New Mexico's 400-mile stretch of Route 66 is also lined with historic Native American sites, such as the Pueblo of Laguna, the largest of the Keresan pueblos.

Spring through fall is the best time to travel Route 66. Remember that while many road trips listed are clearly delineated from start to finish, Route 66 isn't indicated as a single route on contemporary maps, so you'll want to use a resource like Historic 66 to get turn-by-turn directions.

Great River Road National Scenic Byway: Minnesota to Louisiana

• Best time to go: Fall or spring for the best weather

What the Pacific Coast Highway is to the Pacific Ocean, the Great River Road is to the Mississippi River. Starting in Itasca State Park in Minnesota and ending near New Orleans, the Great River Road spans nearly the entire width of the U.S., stretching more than 2,000 miles.

Like Route 66, it's not just one road but rather a series of roads that follow the eastern and western sides of the Mississippi River through Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas and Mississippi.

Each state along the Great River Road has its own interpretative center that educates travelers about the route's history: In Mississippi, you'll find Vicksburg National Military Park; Missouri is where you can check out the Mark Twain Boyhood Home & Museum; and in Iowa, there's Effigy Mounds National Monument, home to more than 200 prehistoric mounds constructed by pre-Columbian Mound Builder cultures.

If you start out West

Pacific Coast Highway: California to Washington

Best time to go: Late spring when wildflowers are in bloom

While the Pacific Coast Highway is considered an iconic California road trip, we'd argue that it's actually worth it to traverse the entire 1,650 miles from San Diego to Olympic National Park in Washington.

Sweeping views from high above the blue-green Pacific Ocean make the PCH one of the most beautiful road trips in the nation, and there are plentiful park options along the way. Point Lobos State Natural Reserve is known for viewings of sea otters, seals and whales, while Garrapata State Park is renowned for its coastal redwood groves. Just south of Garrapata is the most photographed landmark of the PCH: Bixby Creek Bridge, one of the world's tallest single-span concrete arch bridges.

From there, the largest concentration of stops is in and around the coastal area of Big Sur, California. Enjoy a glass of wine, lunch or both at Nepenthe, where spectacular views of over 60 miles of shoreline await. You can also grab a soft serve ice cream or coffee at Coast Big Sur before pausing at the McWay Falls overlook or taking a peek at the sunset through Keyhole Arch on Pfeiffer Beach.

Just past the southern end of Big Sur is Hearst Castle, newspaper magnate William Randolph Hearst's 1920s-style Spanish Colonial Revival mansion. It is one of the most popular attractions on California's central coast.

Historic Columbia River Highway: Oregon

• Best time to visit: Spring through fall, with fall offering the most colorful views

Oregon's Historic Columbia River Highway dates back to 1913; it was the first planned scenic highway in the U.S. This 75-mile route begins in Troutdale (an eastern suburb of Portland) and ends in The Dalles — it can be explored in a day.

Must-see features of the stunning thoroughfare include numerous waterfalls, such as Shepperd's Dell Falls and the 620-foot-tall Multnomah Falls, as well as scenic vistas like Chanticleer Point lookout and Crown Point (one of the most photographed spots along the Columbia River).

If time permits, stop at some historical landmarks that demarcate explorers Meriwether Lewis and William Clark's journey, such as Rooster Rock State Park, Cascade Locks Historical Museum and the Rock Fort Campsite in The Dalles.

US Route 89: Through Arizona, Utah, Wyoming and Montana

• Best time to visit: Any time of year

Though no longer an official U.S. national park road, U.S. Route 89 (formerly known as the National Park-to-Park Highway) is a great option for those wishing to take the road less traveled. Start this journey in Arizona, and move through Utah and Wyoming until you get to Montana.

As you travel U.S. Route 89, you'll pass more than 150 towns, cities and reservations, as well as seven national parks (including the Grand Canyon, Glacier and Yellowstone) and three geographic regions (Basin and Range National Monument, the Colorado Plateau and the Rocky Mountains).

While going from end to end is an option, those looking for a quicker route can consider a shorter stretch that takes you from Jackson Hole, Wyoming, to Glacier National Park.

Going-to-the-Sun Road: Glacier National Park, Montana

• Best time to visit: When the snow has melted and the road is open, usually from the first of June until October

The 50-mile Going-to-the-Sun Road is the only road through Glacier National Park. It's also one of the narrowest and most winding thoroughfares on this list, rewarding travelers with some of the country's most epic landscapes.

You might even spot some mountain goats from the Jackson Glacier Overlook and the route's highest point, the 6,646-foot-tall Logan Pass. The road — which is busiest from late June through late August — also runs by several lakes, including Lake McDonald and St. Mary Lake, and majestic waterfalls like McDonald Falls and Bird Woman Falls.

If you start in Maine

US Route 1: Maine to Florida

• Best time to visit: Late September or early October (if you start this route in New England)

Beginning near the Canadian border at Fort Kent, Maine, historic U.S. Route 1 spans nearly 2,500 miles along the Atlantic coast, passing through a slew of East Coast destinations — including New York City, Philadelphia, Baltimore and Washington, D.C. — before ending in Key West, Florida.

You'll find Colonial towns such as 370-year-old Portsmouth, New Hampshire, a harborside locale full of charming restaurants, inns and shops, as well as Salem, Massachusetts, infamous for its historic (and tragic) witch trials. Additionally, drivers can check out Newport, Rhode Island, known for its Gilded Age mansions, including The Breakers, the lavish summer "cottage" of Cornelius Vanderbilt II.

Farther south, U.S. Route 1's highlights include northern Virginia's Mount Vernon, the one-time home of George Washington, and South Carolina's 45,000-acre Carolina Sandhills National Wildlife Refuge.

Acadia All-American Road: Maine

• Best time to visit: Late fall to avoid the crowded summer months and enjoy colorful foliage

Though you could complete the Acadia All-American Road in half a day, there's much to see along its 40 miles through Acadia National Park. The scenic byway starts at U.S. Route 3 just south of Trenton and crosses the bridge onto 108-square-mile Mount Desert Island.

Highlights of the Acadia All-American Road include Bass Harbor Head Light Station, a lighthouse dating back to the mid-1800s, and Cadillac Mountain, the park's highest point. The latter includes interconnected carriage roads and old stone bridges, most of which are closed to cars.

To explore these areas, bring your bicycles or rent them in the island's seaside community of Bar Harbor. For food, there's nothing better than the fresh seafood at the Thirsty Whale Tavern.

Bottom line

No matter which routes you choose to traverse, remember that the journey isn't solely about the main highlights; the lesser-known destinations you find along the way are an equally important part of the road trip experience.