WASHINGTON — As New Year’s Day approached 150 years ago, all eyes were on President Abraham Lincoln in expectation of what he warned 100 days earlier would be coming — his final proclamation declaring all slaves in states rebelling against the Union to be ‘‘forever free.’’

A tradition began Dec. 31, 1862, as many black churches held Watch Night services, awaiting word that Lincoln’s Emancipation Proclamation would take effect amid a bloody Civil War. Later, congregations listened as the president’s historic words were read aloud.