The Mexican-American War began in 1846. To find the answer to this question, you can use various resources such as history books, online articles, or search engines. One way to find the answer is to use a search engine and type in "Mexican-American War start date." The search results will likely provide reliable sources that mention the year the war began. Another option is to consult a history book or online article specifically about the Mexican-American War. These resources will provide a detailed account of the events surrounding the war, including the year it started.
