The Guardian is a major international newspaper, with a long history, and a good reputation. They are more recently famous for breaking the story about the leaks by Edward Snowden. The paper is owned by a Trust, whose sole purpose is to fund the paper, giving it financial and editorial independence.
They accept submissions from freelance writers in the United States. They pay 310.68 GBP, or ~$450 USD for commissioned work. They pay 90 GBP or $130 USD for blog posts.
They publish articles in a wide variety of categories, including essays, commentary, news, investigative journalism, politics, and pop culture. Each section of the paper has an editor available for contact.
For writers new to the paper, they may ask for the article on spec – without promise of payment, unless published.
To learn more, read their submission guidelines.