First found in county Roscommon, where they held a family seat from very ancient times.

A massive amount of Ireland's native population left the island in the 19th century for North America and Australia in hopes of finding more opportunities and an escape from discrimination and oppression. A great portion of these migrants arrived on the eastern shores of the North American continent. Although they were generally poor and destitute, and, therefore, again discriminated against, these Irish people were heartily welcomed for the hard labor involved in the construction of railroads, canals, roadways, and buildings. Many others were put to work in the newly established factories or agricultural projects that were so essential to the development of what would become two of the wealthiest nations in the world. The Great Potato Famine during the late 1840s initiated the largest wave of Iris immigration. Early North American immigration and passenger lists have revealed a number of people bearing the name Kalen or a variant listed above: Peter Callan who settled in Cape Elizabeth, Maine in 1683; Charles Callan settled in Delaware in 1772; Alexander Callan settled in Wilmington, N.C. in 1774.

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