Liu is serving an 11-year sentence for writing an appeal for multiparty democracy.
About 50 gathered Friday at the Victims of Communism Memorial. It features a statue inspired by the "Goddess of Democracy" that Chinese students built during the 1089 Tiananmen Square uprising.
Ohio Rep. Dennis Kucinich joined the crowd, saying great nations have a responsibility to protect human rights. He says China must remember "the human spirit cannot be suppressed."
Jonathan Cao, of the Chinese Coalition for Citizens Rights, said Liu expressed his political views but China won't allow free speech.