Do you need to put 1 in front of American numbers when texting off an American number?

In general, if you are within North America (USA, Canada, and certain Caribbean and nearby islands), texting another North American mobile phone (cell phone), you can just enter the area code and number without the '1', or you can enter the number in international format. By coincidence, the country code for North America is +1, so a North American number in international format will look something like +1 262 555 0123.