Traveling the country, she discovered even more versions of strength: girls fighting cancer and standing up to bullies in the lunchroom; female football players and ballet dancers whose powers could rival a superhero's.
"Strong, to me, is facing something that scares you and doing it anyway. Courage isn't the absence of fear. It is being afraid and doing it anyway," Parker said.
All those strong girls fiercely going for whatever they want, gender stereotypes be damned, are part of "Strong is the New Pretty," Parker's first book
, releasing March 7.
CNN asked Parker about her new project. Her answers have been edited for space.
CNN: Why did you start posting images to social media?
Kate T. Parker: I was photographing my daughters, Ella (now 11) and Alice (now 8), every day. I noticed that the images that were strongest and most meaningful to me were the ones where the girls were being themselves, whatever that was at the moment: dirty, feisty, silly, sassy, angry, funny, loud and louder. They didn't need to pose a certain way or smile for the camera or brush their hair to be beautiful.
I wanted my girls to know that those images that captured their true personalities showed their beauty. The images turned into a tool I could use to combat the messages the media often sends to girls and women: that beauty is a particular hairstyle, size or outfit.
Wild girls should be allowed to be wild. Introspective girls should be allowed to be quiet. Funny girls should be allowed to be funny. Girls who are all these things should be all these things and should be allowed to find out who and what they are without boundaries.
Giving girls the space and time and support to find out just who they are, what they like and, ultimately, what they love is a key job as a parent or mentor.
CNN: What did you learn from photographing girls all over the country?
Parker: As the project grew, I learned that strength doesn't always come in one package, and it doesn't always manifest itself the way it does in my girls.
Strength isn't always loud and feisty. Strength can be in the face of a musician creating music because it is inside of her. Strength can be changing tables in the lunchroom because your "friends" weren't actually your friends. Strength can be meeting a cancer diagnosis with unrelenting positivity.
I continue to be so inspired by the girls and young women who are featured between this book's covers. These girls are the faces of a new generation of women who don't need someone to tell them that "it is what is inside that counts." They already know it.
CNN: What is beautiful about the girls in your book?
Parker: The girls in this book are all amazing and strong and beautiful, and they're not alone. There's something unique, powerful and worthy in everyone. My job as a photographer is to find this "thing" and capture it, but I'd encourage everyone to try to do this for themselves and for others. You don't need to be a photographer to recognize beauty in yourself and others.
CNN: What stereotypes are you fighting?
Parker: Even today, girls are told that they should be quiet and sit down to allow space for the boys to take charge. That makes me so angry. I want our girls to know that who they are, just as they are, is enough.
Too often, our strength is taught or discouraged out of us as we grow up, but it's like a muscle that needs exercise. The more you use it, the easier and more natural it becomes -- even if you have to start by pretending. While on the journey -- you can do this even as an adult -- start small by trying things you normally wouldn't and go from there.
I hope that this message grows. I hope girls and women believe -- and retain that belief -- that they are amazing and strong and powerful. I hope our government hears this, and I hope my daughters and their daughters don't have to keep fighting this same fight.
CNN: How do you parent knowing that bias exists?
Parker: We stress the importance of being a good person: Being kind, being honest, keeping your word. We remind them that your value is determined by how you treat others rather than how you look or what you're wearing.
Our girls are under so much pressure -- pressure to look, feel and be happy and perfect all the time. Social media encourages an unrealistic level of perfection that is unhealthy.
Women and girls are strong. That's not new. But convincing them that their strength has value and is worth expressing is something that can take some work.
Beauty and power and strength come from being confident in your own worth, but it's a message that bears repeating. While every generation of girls is dealing with similar stereotypes, this generation of young girls are facing new pressures from the internet and social media to look, act and be perfect. No one is happy all the time, that no one's life is perfect, and we are all just in this together trying to figure it all out.
I wanted this book and its message to be a little oasis for girls. They can look at it and read it and see that they don't need to change, add a filter or be someone or something else to be beautiful. They already are.