Twenty-one years after President George H.W. Bush signed the Americans with Disabilities Act (ADA) into law, public spaces, education and employment opportunities are more prevalent than ever for people with disabilities.

Before the law, there were no mandates for public spaces, schools or companies to accommodate people with disabilities, mental or physical, according to the Council on Contemporary Families.

But now opportunities and accessibility are required, and discrimination is prohibited.

"As more students with various developmental delays and disabilities are given the opportunity to go to school with their peers and be taught to their own Individualized Education Plan — an IEP is a free resource for school-aged children entering the public school system — old limitations are also slowly being replaced by new expectations for children with intellectual details," the Council said in a statement today.

It extends into higher education, too. There are at least 69 four-year college programs in the U.S. that are designed for those with intellectual disabilities, it said.

Yesterday, in a proclamation acclaiming the impact the ADA has had in the U.S. since 1990, President Obama said it is "one of the most comprehensive pieces of civil rights legislation in our nation's history."

With one in five Americans living with a disability, the contributions they make to their communities and to society are innumerable, Obama said.

"They are our family members and friends, neighbors and colleagues, and business and civic leaders. Since the passing of the ADA, persons with disabilities are leading fuller lives in neighborhoods that are more accessible and have greater access to new technologies. In our classrooms, young people with disabilities now enjoy the same educational opportunities as their peers and are gaining the tools necessary to reach their greatest potential."

The ADA made the U.S. the first country in the world to sign into law equality for citizens with disabilities. Now, Obama said, the U.N. ratification of the Convention on the Rights of Persons with Disabilities, which promotes equality and assures the same rights and opportunities to those with disabilities, would provide a greater platform to motivate other countries to implement the same rights and opportunities for their disabled citizens.

One year ago, on the 20th anniversary of the ADA, Ben Mattlin, a man with spinal muscular atrophy who lives in Los Angeles, wrote about his experience of life before and after the ADA became law for NPR.

It was difficult for his parents to find a school willing to accept a disabled child, which Mattlin thought was because he wasn't smart enough. He ended up at Harvard in 1980, where it was hard to get around campus, and he wasn't allowed to have a roommate for fear he would impair their educational experience, Mattlin said.

The discrimination he encountered in college extended into employment after graduation where interviewers assumed he wouldn't be able to perform basic tasks like photocopying and wouldn't hire him.

He was 27 years old when the ADA was signed into law.

"It didn't get me a job … It identified a 'reasonable accommodation' from an 'undue hardship — a critical distinction for employers and public places alike," he said. "Now, the ADA's impact is everywhere: wheelchair lifts on city buses, signs in Braille, sign-language interpreters. Many young disabled people are growing up with a marvelous sense of belonging, entitlement and pride I never had."

Though he recognized that there is still a long way to go to improve the lives of people with disabilities, the ADA has made it an issue that is impossible to ignore.

"So now people should understand we're just part of the human landscape," Mattlin said. "We're here to stay."