Paris has a large muslim population. The exact number is not known because the French census does not ask about religion but it is estimated that in France between 5 - 10% are muslim.
A great many of the immigrants came in the 1960's and 70's to fill jobs at a time of a shortage of labour. But the muslin community in Paris goes back further. The Great Mosque in Paris' 5th arrondissement was built between 1922 and 1926 as thanks to the muslims who fought for France at the battle of Verdun in 1916 in which 28,000 muslim soldiers (mostly Algeriens and Morrocans) were killed.
At the moment there is the fast of ramadan and it's actually a good time to stroll through one of the muslin communitities in Paris. For example walk around the beween Metro Menilmontant and Belleville in the afternoon and it's very lively with many stalls on the streets selling North African ramadan special food for the end of the fast such as dates, ricotta style cheese, halva and much more. Many of the local restaurants do special "ramadan menus" which you can enjoy even if you're not muslim.