Although now past their best for the year, Mars and Saturn both remain prominent early evening objects during September. After sunset from mid-northern latitudes the planets can be seen for a few hours above the south-southwest horizon before setting. From further south the visibility is much better. For example from Sydney, Mars and Saturn appear high in the northern sky at sunset, remaining visible until around midnight.
On September 8th, the waxing crescent Moon will be about 4 degrees north of Saturn. The following day the Moon, now first quarter, passes 8 degrees north of Mars. Both days offer nice opportunities to spot the Moon, the two planets and also first magnitude red supergiant star Antares (α Sco) together in the early evening sky.
The images below show the view during the evenings of September 8th and 9th from New York. Mars shines at mag. -0.2, Saturn +0.5 and Antares +1.0. From other mid-latitude northern locations the scene will look similar.