[1] In 1901, López set out on a nearly two-year journey across the United States, petitioning for the freedom of three of her brothers who had been imprisoned by the American military in the Philippines.

Throughout her stay in the United States, López drew attention to the Philippine independence movement, became the first Filipina to ever enter the White House, and spent time studying at Wellesley College.

[9] Unlike some of her more activist brothers, López did not overtly adopt an anti-imperialist, pro-independence stance as the United States, which took over the Philippines in 1898 following the Spanish-American War, became increasingly imperialistic.

[13] Sixto, a loud advocate of Filipino independence, was inspired by the writings of José Rizal, and he himself also wrote and distributed anti-American imperialism literature.

[18] Clemencia López, then 26 years old, resolved to travel to the United States herself to plea for her brothers’ freedom in person to the American President.

López first visited her brother Sixto in Hong Kong for two weeks, and then set out for the United States in an unprecedented international voyage for a young Filipino woman.

[21] In the United States, López stayed with Fiske's sister, Cornelia Lyman Warren, who was an activist herself working for the settlement movement.

López's close connection to the Warren family allowed her to build an anti-imperialist network in the United States, especially with like-minded women who were eager to bring reforms to society.

While López's mission to free her brothers ultimately failed, she did briefly meet President Theodore Roosevelt in March 1902, purportedly making her the first Filipina to ever enter the White House.

On 23 April 1902 George B. Cortelyou, President Roosevelt's secretary, wrote to López that, regarding the imprisonment of her brothers, "there appears to be a consensus of opinion that no injustice was done".

[24] As it was, the López brothers were freed a few weeks later due to an unrelated United States Army decision that guerilla fighters in the Philippines were no longer a significant threat.

In front of an audience of three hundred, many of whom had never seen a Filipino in their lives, López, speaking in Spanish, said:[34]You can do much to bring about the cessation of these horrors and cruelties which are today taking place in the Philippines, and to insist upon a more human course.

[41] While López did not earn a university degree, she did benefit from access to notable scholars, including economist and historian Katharine Coman, as well as opportunities to improve her English language skills, which allowed her to better communicate with American audiences.

[47] López's actions throughout her life challenged racist and sexist stereotypes prevalent in the early twentieth century United States.

[53] Clemencia Lopez was depicted as one of the three largest portraits painted at the central part of the 22' x 60' mural honoring her as one of the three "Mothers of History".

[55] In 2018, the Philippines Department of Foreign Affairs unveiled ten portraits of prominent Filipinos in history, including Clemencia López.