On the 17th of April 1966, a huge demonstration took place in West Belfast to mark the 50th anniversary of the 1916 Easter Rising.
[O]n 17 April, one of the biggest parades ever witnessed on the Falls took place. Paisley announced he would hold a counter-march from the Shankill to the Cenotaph and the Ulster Hall, this would pass close to where the republican parade was to start. As a result the Stormont government banned a train carrying republican supporters from Dublin, set up stringent border checks on vehicles and further increased the strict security measures placed upon the parade on the Falls Road. … Up to fifty thousand spectators watched, many waving Tricolours, as twenty thousand people paraded to Casement Park. Among those who took part were the Belfast Trades Council, a number of trade unions, the old IRA, the Wolfe Tone Clubs, the Irish National Foresters and the GAA. A small bomb exploded in a telephone box near the Milltown Cemetery, but otherwise the day passed off peacefully. Jarman, N. and Bryan, D., 1997. From Riots to Rights: Nationalist Parades in the North of Ireland. Coleraine: Centre for the Study of Conflict, University of Ulster.
The United Irishman report the following month includes the text of the oration at Casement Park by Seamus Costello: