The club was founded in 1880. The Swifts won the first
Linlithgowshire Cup - also known as Lord Rosebery's Cup - in 1884–85 unusual circumstances. In the semi-final, the Swifts beat
Durhamtown Rangers, who then protested on the basis that Mossend was not actually in
Linlithgowshire, and so the club should not be allowed to enter. Mossend pointed out that it had been invited to join the association and paid its scrip; the Rangers produced a letter from
Lord Rosebery setting out the terms of the competition, namely it was for clubs in the county only. The compromise was to let the Swifts complete the tournament, which his Lordship considered "quite satisfactory", and the Swifts beat
Armadale 3–2 at
Bo'ness in the final. For the 1885–86 tournament, the Linlithgowshire Association simply "forgot" to invite the Swifts to defend the trophy, which had not had the Swifts' name inscribed thereon. The club joined the
Scottish Football Association in August 1886 and entered the
Scottish Cup from
1886–87. Its first season as a senior club saw it win the
King Cup (for members of the East of Scotland FA), beating
Burntisland Thistle 4–1 in the final; the club went behind in the first five minutes, but goals from Howieson, Boyd, and Ellis put the Swifts 3–1 up at the break, and the Swifts employed a tactical change - Howieson stepping back to midfield, to make two banks of four in front of the full-backs - to preserve the lead. Ellis rounded off the scoring with a long, low shot late on. The club's best run in the national competition came in
1888–89, reaching the final 16; in the first round the Swifts caused a major shock by defeating
Hibernian 2–1at Mossend Park in front of a crowd of 2,000. The club was eliminated in the fifth round at
Dumbarton; the club was unlucky as the original tie was declared a friendly because of a waterlogged pitch, and, as the Swifts had drawn 1–1 (albeit in a match of one hour's duration), it lost the potential to host the replay. The Swifts protested its defeat in the re-played tie on the grounds of roughness on the part of Dumbarton, but to no avail; although the referee reported Dumbarton's Madden to the Scottish FA for repeated tripping, he also reported the Swifts' Ellis and Mackay for kicking their opponents in the stomach, Mackay kicking Stewart so hard that Stewart was knocked unconscious for an hour. Already by 1891 there was talk of a possible merger with
West Calder F.C. on the basis that West Calder could not support two football clubs. Nevertheless, the Swifts continued successfully for a number of years, including winning the King Cup and East of Scotland Shield (the new name for the Edinburgh Shield) in 1895–96, both times beating
Polton Vale in the final. The club had an easy 4–1 in the former, in front of 2,000 spectators at
Bathgate; a Vale protest was dismissed for lateness. The Shield was a different matter, the Swifts apparently losing 2–1 at
Tynecastle Park, but a protest that Vale's left-back Oag and inside-right Phillips for "professional irregularities" was upheld. In the re-played final at
Easter Road, the Swifts again won by 4–1. The merger with finally took place in May 1903, the merger creating a new club,
West Calder Swifts F.C.; although the name was a merger of the two teams' names, the combined club played at West Calder's ground, wearing West Calder's kit. The club's trainer however was the Mossend Swifts trainer David Bowman, who finished with 23 years' service at both sides. ==Colours==