Born on a ship in the North Sea, Kempfer was adopted by a Norwegian family that immigrated to the United States in 1885.

Johannah Josephine was born on December 22, 1880, in the North Sea on a ship sailing under a British flag.

Ole and Martha Jensen, a shipbuilder and his wife who had recently lost their only child, adopted Johannah in March 1881.

[3] In 1889, the Jensens moved to Otter Tail County and, being very poor, squatted a piece of property that belonged to the railroad.

[1] Kempfer was active in her community, helping to form a farm improvement club and organizing church socials and quilting bees.

She campaigned throughout the county, traveling in a Ford Model T.[3] In November she was elected as one Minnesota's first four woman legislators alongside Mabeth Hurd Paige, Sue Metzger Dickey Hough and Myrtle Cain.

She and Mabeth Hurd Paige introduced legislation in 1925 that protected the Showy Lady's slipper, Minnesota's state flower.

In 1923, she joined her fellow women legislators and introduced a bill extending rights to children born out of wedlock.

[3] Following the repeal of prohibition of alcohol, she supported local-option laws and the issue came up repeatedly in her subsequent campaigns.

[2] She died at the Fergus Falls hospital on September 27, 1943[1] due to complications from a tumor which was too close to her aorta to be removed via operation.