One of the big mistakes that many developers make is accepting a low or barely acceptable initial salary in the hopes of making up the difference with raises later. The reality I have found, and probably many people will agree with, is that it is very hard for a non-executive/manager to make up for a small starting salary from within a company, especially with the same role. A good salary increase for performance is 10%, but it would still take over 4 years of the maximum performance increase to reach $70K from $47K. And that assumes that your contributions are acknowledged and you get the maximum performance increase for it. Even changing positions within the organization may not bridge the gap as much as you would like. I remember a very smart guy at a previous company that started at a low salary. Due to his competence, he was moved/promoted to a different department that had much higher average salaries than the one he came from. The problem was a company policy that capped salary increases when moving from one job to another at 15% of your prior salary. This struck me and him as completely counterintuitive. The company was willing to pay someone off the street that had much less institutional knowledge much more simply because they were new.
So the final question is, is $47K an acceptable salary for your area? Did you accept it because you were desperate or because you truly thought $47K was a fair salary? The moral of the story is that if you really feel like you deserve $70K - $90K, then the only practical way you're going to get it is by changing jobs or truly committing to your current company and getting multiple significant promotions from within. Your mileage may vary depending on the bonus/promotion structure of your company but don't count on just doing a good job and being loyal to cut it.