There are 224 state-level, ballot-qualified political parties in the U.S. How does that compare with prior years?

Although there are dozens of political parties in the United States, only certain parties qualify to have the names of their candidates for office printed on ballots. In fact, in 2019, there are 224 ballot-qualified, state-level political parties in the 50 states and Washington D.C..
Of these, 51 are Democratic Party affiliates and 52 are Republican Party affiliates. Three minor parties are recognized in more than 10 states: the Libertarian Party (37 states), the Green Party (26 states), and the Constitution Party (14 states).
The number of ballot-qualified, state-level political parties in 2019 is the second-highest since 2013, when we first began tracking this information. The 2018 total—229 parties—ranks first. Here are the number of relevant political parties each year since 2013:
• 2013: 198
• 2014: 220
• 2015: 221
• 2016: 214
• 2017: 215
• 2018: 229
In order to qualify for ballot placement, a party must meet certain requirements that vary from state to state. For example, in some states, a party may have to file a petition. In other states, a party must organize around a candidate for a specific office; that candidate must, in turn, win a percentage of the vote in order for the party to be granted ballot status. In other states, an aspiring political party must register a certain number of voters.
For more information, including a complete state-by-state breakdown of ballot-qualified parties, see this article.