Dower is often seen as an antiquated, unnecessary law that complicates real estate transactions because it provides even a non-title holding spouse with a real property interest. Dower was intended to help women in an era where they were not permitted to own property. Dower provided them income from their husbands' real estate if he passed.  Even after women were allowed to own property, dower remained as a means of balancing out economic disadvantages they faced.  

According to Blacks Law Dictionary "dower" is defined as:

dower. At common law, a wife's right, upon her husbands death, to a life estate in one-third of the land he owned in fee.  With few exceptions, the wife could not be deprived of dower by an transfer made by her husband during his lifetime.  Although most states have abolished dower, many states retaining the concept have expanded the wife's share to a life estate in all the land that her husband owned in fee.  

 And, if you are curious, the husband's counterpart was known as "curtesy."

curtesy.  At common law, a husband's right, upon his wife's death, to a life estate in the land that his wife owned during their marriage, assuming that a child was born alive to the couple.  This right has been largely abolished.  Also spelled "courtesy."

I do not believe that any state still recognizes curtesy, but all of the remaining states that recognize dower have extended it to include husbands, as well as wives.  Ohio's dower statute, for example, provides that "a spouse who has not relinquished or been barred from it shall be endowed of an estate for life in one third of the real property of which the consort was seized as an estate of inheritance at any time during the marriage." (for the full statute see R.C. 2103.02).

Michigan's statue was different; they retained the traditional dower pertaining only to wives. The statutes provided that "the widow of every deceased person, shall be entitled to dower, or the use during her natural life, of 1/3 part of all the lands whereof her husband was seized of an estate of inheritance, at any time during the marriage, unless she is lawfully barred thereof."  MCL 558.1.  

After the Supreme Court held that same-sex marriage was a Constitutional right, the Michigan legislature reviewed all of their statutes that might be problematic because they contained gender specific terms relative to married couples.  (See Analysis of the Michigan Constitution and Statutes Affected by Obergefell v. Hodges).  A dower right for a "widow" only, in the lands of her "husband" was clearly a potential problem that could have spurred many lawsuits.  So, the legislature added MCL 558.30:

Sec. 30. (1) Notwithstanding sections 1 to 29, and except as otherwise provided in subsection (2), a wife’s dower right is abolished and unenforceable either through statute or at common law.

(2) This section does not apply to either of the following:

(a) A widow’s dower elected by a woman whose husband died before the effective date of the amendatory act that added this section.

(b) If a widow’s husband died before the effective date of the amendatory act that added this section, the widow’s right to elect dower under section 2202 of the estates and protected individuals code, 1998 PA 386, MCL 700.2202.

 As of April 6, 2017, the effective date of the new law, dower in Michigan is no more... except for widows whose husbands pass before then.