Our dept chair of General Surgery was also boarded in Critical care so I figured that it might not always be necessary to do the residency necessarily before board certification...
In backwater areas (population less than or equal to 50,000) it is not uncommon for Family or Internal medicine doctors to staff ERs. So I was curious that if one were to do a residency in internal, work as a hospitalist, could they then also sit for ER boards if they were comfortable. In Bradford, PA (home of the world famous Zippo lighters), for example, there are a number of ER docs who are not even board certified in ER, and they all make over 200k for 10 - 15 days per month of work.