What can I do if I recently took maternity leave from my job of 3 years and when I came back my pay was decreased?

First, be careful about assuming  that a decrease in pay lets you quit your job and file for unemployment: while sometimes you are considered  to be "constructively terminated" if your job was made *so* much worse that you were effectively fired, the standards for this are very high. For example, I doubt that even a 20% or 25% decrease would automatically qualify for this. You are probably best off looking for a new job while still working here--it might, but you could  not count on it. (That also, by the way, is the advice that most HR Directors would give you; people who are out of work tend to be less attractive to new employers--that may be unfair, but that's how it seems to be.)

Second, you say the "business was sold." If the new owner bought the LLC or corporation, it is possible that you may have a claim for discrimination (against a woman; against someone with a disability--pregnancy can count as a temporary disability) and you should speak with your state equal/civil rights agency. That's because in this case, it's the same entity as the one you took your leave from.

Howver, if the new owner did not buy the actual LLC or corporation, but instead bought only the assets (e.g. name, good will, intellectual property, physical assets, customer list, etc.) then this is a new business legally; and as a new business would not be obligated to offer *any* employees of the old company jobs, even though they plainly could and did. As a new business, they would have substantial discretion whether to hire you and in what capacity, and you woud be unlikely to have a claim.

First, be careful about assuming  that a decrease in pay lets you quit your job and file for unemployment: while sometimes you are considered  to be "constructively terminated" if your job was made *so* much worse that you were effectively fired, the standards for this are very high. For example, I doubt that even a 20% or 25% decrease would automatically qualify for this. You are probably best off looking for a new job while still working here--it might, but you could  not count on it. (That also, by the way, is the advice that most HR Directors would give you; people who are out of work tend to be less attractive to new employers--that may be unfair, but that's how it seems to be.)

Second, you say the "business was sold." If the new owner bought the LLC or corporation, it is possible that you may have a claim for discrimination (against a woman; against someone with a disability--pregnancy can count as a temporary disability) and you should speak with your state equal/civil rights agency. That's because in this case, it's the same entity as the one you took your leave from.

Howver, if the new owner did not buy the actual LLC or corporation, but instead bought only the assets (e.g. name, good will, intellectual property, physical assets, customer list, etc.) then this is a new business legally; and as a new business would not be obligated to offer *any* employees of the old company jobs, even though they plainly could and did. As a new business, they would have substantial discretion whether to hire you and in what capacity, and you woud be unlikely to have a claim.