iOS has a 29.5 percent share of the US smartphone market, up from 28.1 percent in October 2011, according to figures from comScore.
However, Android still dominates the sector and also increased its share in the same period, from 46.3 percent in October last year to 48.6 percent.
The latest figures, taken in January 2012, show RIM's market share to have decreased from 17.2 percent to 15.2 percent.
Microsoft also suffered a poor three months, slipping from a 5.4 percent share to 4.4 percent. Symbian's market share also slightly decreased from 1.6 to 1.5 percent.
According to comScore's figures, there are now more than 100 million smartphones in the US, representing growth of 13 percent in the last quarter.
Overall, 234 million Americans aged 13 or older use a mobile device, with Samsung ranked as the top mobile phone manufacturer with a 25.4 percent market share in January 2012, down 0.1 percent from October 2011.
LG is in second place, with 19.7 percent, down from 20.6 percent in October 2011, while third-placed Motorola dropped from 13.6 percent to 13.2 percent in the same period.
Apple, meanwhile, grew its US mobile phone market share in the same period from 10.8 percent to 12.8 percent to maintain its fourth place in the rankings. RIM was in fifth place, with its share stable at 6.6 percent.