The tax reform of 1986 eliminated the marriage penalty at the lower income levels. The marriage penalty did still exist, but only at higher income levels.
This blog post gives a couple of examples of how taxes worked for married couples in 1920.
The treatment of marriage in the tax code was different 100 years ago than it is now.
The IRS has 7 tax tips for the recently married. From IRS Summertime Tax Tip 2011-20: Notify the Social Security Administration Report any name change to the Social Security Administration so your name and Social Security number will match when you file your next tax return. File a Form SS-5, Application for a Social Security Card, [...]