After decades of farm specialization, re-integrating crop and livestock farming systems is being reconsidered as a key step toward sustainable agriculture. The relative profitability of Maine farms integrating crops and livestock is compared to non-integrated or conventional farms. Crop and livestock integration in Maine occurs through either diversified on-farm integration or, more commonly, through coupled interactions between specialized crop and livestock producers. Potato and dairy systems coupled for only 2 years (short-term) had greater profitability compared to conventional systems. Profitability increased in the short term in two ways. First, potato farms grew more of their primary cash crop. Secondly, dairy farms expanded cow numbers, increasing profitability assuming increasing returns to scale. Coupled systems integrated for more than 10 years (long-term) had more favorable profitability than short-term couplers since greater manure-nutrient credits were taken for potatoes and silage corn. The advantages of potato–dairy integration were even greater if potato yields increased in the long term, as suggested by long-term rotation plot studies in Maine. Even if coupling is more profitable than non-integrated systems, it requires that farms be in close proximity and for farmers to have adequate working relationships and management skills. Despite these challenges to re-integrating crops and livestock, short- and long-term economic benefits may encourage farmers in appropriate areas to consider coupling with other producers.