North Dakota is about 2.2 times bigger than Maine.

Maine is approximately 79,931 sq km, while North Dakota is approximately 178,647 sq km, making North Dakota 124% larger than Maine. Meanwhile, the population of Maine is ~1.3 million people (655,770 fewer people live in North Dakota).
Tip: This to-scale comparison of Maine vs. North Dakota uses the Mercator projection, which distorts the size of regions near the poles.