The new century dawned and Constitution travelled to Dublin for the first time on January 23rd 1900 to play Old Wesley where Constitution won by 8 points to 6.

The final of the Cork Junior Cup brought Constitution into opposition once more against Queen’s College on March 10th. This was the fifth successive year Constitution reached the final, but a defensive mistake cost them the match. Then just before Christmas 1900, new ground was broken when Constitution set out for Wales on their first cross-channel tour.

Constitution reached their first Munster Senior Cup final in 1901. They beat Garryowen, after a replay, and Cork FC on the way to the final. The final was at Turner’s Cross against the holders, Queen’s College, who were more experienced in the arts and strategies of senior cup campaigns and won the day. A new league competition was inaugurated for senior clubs that was to become a vital part of the competitive rugby season in Munster and Constitution duly won in the first two seasons.

When the site of the 1902 Cork Exhibition at the Mardyke was re-developed as a sporting facility, Constitution and Cork County clubs took tenancies, and played the first club match against each other there in September 1904. So began a 50-year association with the first major sporting arena in Cork.

Constitution again reached the Cup final in 1905. They had fought out a tremendous replayed duel with Rockwell and just three days later on Thursday April 13th faced Queen’s College again in the final. From the outset Constitution imposed the pattern of play. The newspaper reports were unanimous in their verdict about the worthiness of the Constitution victory. And so David Desmond was the first Constitution player to lift the Munster Senior Cup as they won 11-3. The stature of the club was further recognised when Cardiff played Constitution at the Mardyke at the end of the season.

While 1905 proved to be a great year in the club’s history, the events of the following season eclipsed all previous happenings. Constitution won the Munster Senior Cup, beating Garryowen 8-0 in the final at the Market’s Field; the newly inaugurated Cork Charity Cup; the Senior League; the Cork Junior Cup and the Tramway Cup. There was no precedent in history for such success by any club.

There were two big international matches in 1905. Ireland played England at the Mardyke in February. Mossy Landers was at full back, with Basil MacLear of Cork County at centre. MacLear scored a try and convert as Ireland won 17-3. The two also played against the first All Blacks touring team, known as ‘The Invincibles’, at Lansdowne Road in December. Three further Constitution players were selected for Ireland during the period: R.M.Magrath, O.J.S.Piper and W.F.Riordan. Oliver Piper became the first Constitution player to be selected for the Lions on their tour to South Africa in 1910 playing in one test game.

Constitution reached the Munster Senior Cup final for the third successive year in 1907 defeating Rockwell and Lansdowne on the way. The final against Garryowen went to a replay before Constitution prevailed 16-3 at the Market’s Field. The three-in-a-row Cup success achieved in 1907 brought an end to a golden period for a talented squad of players and many of those retired to leave the way open for the next generation.

The Munster Junior Cup was introduced in 1908-09 season and Constitution contested the first two finals losing to Crescent College 6-7 and Garryowen 0-3.

In 1910 a fourth Senior Cup victory was achieved by a new squad of players under the captaincy of Bow Hosford when Lansdowne were beaten 8-0 at the Market’s Field to complete a Cup and League double.

P.H.Meade, a prominent businessman and city councillor, was the first member to be honoured with Presidency of the Munster Branch IRFU in 1905-06. He had been instrumental with another Constitution member, John Reese, in developing the Mardyke sports grounds. A number of members, including David Kilroy, served as Hon.Secretary Munster Branch during the period.