Hard to say if there are companies whose decline lasted over a century, but there are definitely some who are close. Consider the East India Company which was

Hard to say if there are companies whose decline lasted over a century, but there are definitely some who are close. Consider the East India Company which was established in 1600 and lasted until the late 1800s. In my native Canada, the Hudson's Bay Company was granted a charter in 1670 and at one point owned half the country. It has been struggling for very nearly 100 years and I think you could say that it has been on a downturn for at least 150 years.