Mackwelung has been described as the "founder of formal education" on the island of Kosrae.[2] Although she had been encouraged to stay in the United States, where she was told that "even though your skin is dark" she could have been admitted to nursing school,[3] in 1932 she returned to her native Micronesia, where she taught first on Jaluit and then at the Mwot Protestant Mission School on Kosrae.[2][4][5] After eight years there, she spent three years teaching at a Japanese school on the island.[2][4]
In the post-war period, Mackwelung took on a greater role in Kosrae's education system, establishing a teacher training program and setting up the islandwide school system.[2][5] In 1947, she became the island's superintendent of schools.[2] Then, in 1952, she became Pohnpei's adult education supervisor.[2][5]
She promoted women's roles in Micronesian society, saying in 1971, "If you ask me what Micronesia needs the most, the answer would be that we need more women educated."[2][3] One local publication described her as "the first Micronesian woman to take on a public career in addition to the traditional role of homemaker."[2][4]
Mackwelung became well known for her work beyond Kosrae, particularly in Pohnpei and the Marshall Islands.[2] In particular, she worked to establish women's organizations across the region, including the Ponape Women's Association in 1955, and beginning in 1957 she served as the economic and political advisor to the administrator of Ponape District, which at the time included Kosrae.[2][6][7] From 1965 until her retirement in 1974, she served as the district's women's affairs officer.[3][5] She also traveled internationally to various seminars and conferences, including as the first woman to receive a United Nations Fellowship in Community Development in 1964.[2][4]