▲Appollo was the first dog on site at the World Trade Center with his handler, Peter Davis of the New York City Police Department. He received medals and awards for his courage and dedication.

▲Bo was the Obama family’s Portuguese water dog.

▲Bo (pictured on the right in the photo) became famous when Obama mentioned him in his 2008 acceptance speech.

▲This giant, sweetheart of a dog made his way into the hearts of his fans during the '90s. The original dog had no problem adapting to his on-screen character as his name was also Beethoven.

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When he was brought back to the US, he was trained to star in silent movies, and was featured in 27 movies in total.

▲Lassie is a fictional character, but arguably the most famous dog in American history. Her story is drawn from acts of bravery and courage during World War I.

▲In the original movie, Lassie was played by a rough collie named Pal. Starting in 1943 and ending in 2007, 10 generations of Pal’s descendants continued to play the character in various movies and shows.

▲Scottish terrier Fala is known for being mentioned in President Roosevelt’s 1944 "Fala" Speech in which he defends himself (and his dog) from allegations that the dog was costing taxpayer's money.

▲He was the only presidential dog to be featured in a statue. He can be seen at the Franklin Delano Roosevelt Memorial in Washington, D.C.

▲No one can forget the heart-wrenching movie, ‘Marley & Me,’ based on the book by the same name. The movie featured 22 different dogs, all working to portray the sweet, yet neurotic Marley.

▲The true story is about a high-strung yellow lab who caused many challenges to his family.

▲This famous cartoon canine has various items named after him, including an underwater vehicle, an Apollo lunar module, and a 280-degree loop in Vietnam’s Mekong River.

▲The fictional beagle is more than 50 years old, but continues to live on in our collective memory.

▲The most recent addition to the list is a modern sensation. She is the famous talking dog, and has almost a million subscribers on YouTube.

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She can say words like “I’m hungry,” “no,” and “I love you.” She has even recorded songs and starred in commercials!

▲He was awarded a silver medal by the National Canine Defence League for his good deed.

▲Russian physiologist Ivan Pavlov (middle) is famous for his experiments with classical conditioning.

▲Lady's mom was able to save her by wrapping her in a blanket and pretending she was a baby.

▲His story was made into a movie starring Richard Gere, called 'Hachi: A Dog's Tale.'

▲Lady, a tiny Pomeranian, was one of three dogs to survive the Titanic sinking in 1912.

▲This black-and-white collie is known for finding the stolen Jules Rimet Trophy in 1966.

▲He used many different dogs in his experiments and had a monument erected in his honor on the grounds of his laboratory at Koltushi.

▲This coming-of-age story pulls at the heartstrings as the two attempt to remain friends against the pressure of Copper's master and the fact that they are natural enemies.

▲This dog was rescued by soldier, Lee Duncan, from a French battlefield during World War I.

▲One day, his owner didn't return after dying from a cerebral hemorrhage. However, every day for nine years, Hachiko continued to wait for his owner at the train station until his own death in 1935.

▲Eddie was played by a Parson Russell Terrier named Moose, and later by Moose's son Enzo.

▲Eddie was Frasier's dog on the popular sitcom of the same name.

▲Toto is Dorothy’s terrier in ‘The Wizard of Oz’ by L. Frank Baum. In the movie, Toto was a male dog, but was played by a female dog, named Terry.

▲Terry was paid even more than the human actors in the film at US$125 per week.

▲The dog who played Benji in the movie, named Higgins, was a rescue from the Burbank Animal Shelter. During his time, he inspired the adoption of more than one million dogs from shelters all over the country, according to Animal Planet.

▲After his service, he received several awards.

▲Hachiko was an Akita dog who lived in Japan during the 1920s and 1930s. Every day, he would wait at the train station for his owner, who was a professor at the University of Tokyo, to return from work.

▲The movie featuring this dog was based on the true story of an Alaskan sled dog who saved the population of his village after an outbreak of diphtheria spread through the area. He led a dog team through arctic blizzards to retrieve medicine from a shipment located 53 miles (85 km) away from the village.

▲Sinbad served 11 years in the US Coast Guard, including during combat in World War II.

▲Benji is a fictional character who has starred in movies from 1974 though the 2000s. The original movie, entitled ‘Benji,’ features a dog who saves two kidnapped children.

▲Scooby is known for his unique and comical voice, extreme fear of ghosts, and his relationship with Shaggy.

▲The original animated series, ‘Scooby-Doo’ continues to be a childhood favorite.

▲Balto’s legend lives on. The famous sled dog earned himself a bronze statue in 1925 in Central Park, NY, and there is an annual sled dog race in Alaska traversing the distance that Balto and his team traveled to retrieve the medicine.

▲Walt Disney's famous dog couple were an American cocker spaniel named Lady and a stray mutt called the Tramp. Their adorable love story will forever be remembered by Disney aficionados.

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Laika, the Soviet Space Dog, was taken from the streets of Moscow in 1957 to be trained for the space program. She became the first animal to orbit Earth in the Sputnik 2, but sadly died due to overheating shortly after launch.

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In total, 350 search and rescue dogs sought out survivors at the Twin Towers site and the Pentagon after the September 11, 2001, terrorist attacks.

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A series of movies and animated TV shows have been created around his canine adventures since then.

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Mickey Mouse’s famous yellow dog will never be forgotten. He makes up the "Sensational Six" (the biggest Disney stars) and is the only one who dresses and acts like a real dog.

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The adorable hound named Copper from 'The Fox and the Hound' is known for his unlikely friendship with a wild fox named Tod.

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Dogs are known as man's best friend for a reason—they capture our hearts like no other animal can. Loyal, smart, and unconditionally loving, dogs have played a critical role in human history for thousands of years. There are some that stand out more than others, whether it be for their acts of courage, heroism, entertainment, or intelligence.

Check out the following list of some of the most famous dogs that have earned a spot in our collective memory and heart.