"Joseph Rainey was a champion for all the people. But most especially he was a champion of the voiceless,” said Lorna Rainey, great granddaughter of Joseph Rainey.

Lorna Rainey is the great granddaughter of an American trailblazer, Joseph Rainey, the first black person to serve in the House of Representatives. But Joseph Rainey's achievement is unknown to most Americans. His great granddaughter is out to change that, and to help to produce a documentary about his life, "Slave in the House."

"I want to tell this story with the honor it deserves," Rainey said.

Joseph Rainey was born into a slave family in South Carolina, but they were able to buy their freedom. He was elected to Congress during Reconstruction after the Civil War, when former slaves were given the right to vote.

He served four terms, until segregationist laws across the south essentially forced Rainey and other black members of Congress from office. It would be 72 years before another African-American would represent the South in Washington.

Rainey is determined that his story not be forgotten, saying he was "opening people's eyes to who was the very first and what it took for him to get there.”

His life story includes refusing to leave a hotel restaurant in South Carolina until he was served, what Rainey called the first sit-in in American history.

"He was the first person to put his actual safety at risk in order to prove a point. He wasn't afraid to do that,” Rainey added.

Rainey still has family heirlooms from the 1800's when her great grandfather took office, including engraved silverware and photocopied pages of his journal. The real one is locked in a vault.

Some of his greatest achievements include advocating for the rights of African Americans, Chinese Americans and Native Americans in the 1870s.

Rainey says she's wanted to tell Joseph Rainey's story ever since she was a little girl when one of his daughters would visit her family in Brooklyn and tell young Lorna about her Great Grandfather.

"Aunt Olive would pull me onto her knee. I was three years old when she would start telling me the stories she would always talk about my Great Grandfather's achievements and she knew well because she was his daughter,” Rainey said.

Rainey said "Slave in the House" is planned to premiere this summer.