Buried deep within the 67-page Defense Appropriations Act of 2010 (H.R.3326) was a

Wounded Knee Massacre, Dec. 29,1890
small section (#8113, to be exact) titled: “Apology to Native Peoples of the United States.” “The United States, acting through Congress, apologizes on behalf of the people of the United States to all Native Peoples for the many instances of violence, maltreatment, and neglect inflicted on Native Peoples by citizens of the United States;” and “expresses its regret for the ramifications of former wrongs and its commitment to build on the positive relationships of the past and present to move toward a brighter future where all the people of this land live reconciled as brothers and sisters, and harmoniously steward and protect this land together.”
The Act was signed by President Obama on December 19, 2009 but never publically acknowledged.
You can read the act here: https://www.congress.gov/bill/111th-congress/senate-joint-resolution/14/text